Wave Power Plant and Transmission

ABSTRACT

A wave energy converter includes a buoy and a transmission unit. In the transmission unit there is a driveshaft, which is driven to rotate either when the buoy rises or sinks, yet always in the same direction. The driveshaft is mechanically coupled to one of the rotating parts of an electric generator and drives this to generate electric current. Further on there is an energy accumulation device, which is also coupled to the driveshaft to accumulate energy when the buoy rises or sinks and the driveshaft rotates and which is then used to drive the generator at the other of the rising and sinking motions. The coupling between the energy accumulation device and the driveshaft can go by the generator&#39;s second rotatable part, the air gap between the generator&#39;s parts and the generator&#39;s first part. The coupling over the air gap gives a torque, which drives the second part to rotate along and which also counteracts the rotation of the driveshaft. The generator&#39;s second part is driven by the energy accumulation device to rotate in the other direction, when the torque from the driveshaft does not exceed the counteracting torque.

RELATED APPLICATIONS

This application claims priority and benefit from Swedish patentapplication No. 0800395-6, filed Feb. 20, 2008, and Swedish patentapplication No. 0802165-1, filed Oct. 10, 2008, the entire teachings ofwhich are incorporated herein by reference.

TECHNICAL AREA

The present invention relates to a wave power plant for extraction ofelectrical energy from motions of water waves, a method of extractingelectrical energy from more or less intermittent mechanical energy, suchas more or less periodical motions in a body, and a transmission forpower plants to be used when such more or less intermittent mechanicalenergy is available.

BACKGROUND

Wave power has a large potential of becoming cost efficient since theenergy density in ocean waves is very high (approximately 1000 timeshigher than in the wind), this allowing small wave energy converters inrelation to the capacity thereof. Furthermore, wave energy is morepredictable than for instance wind power since waves are built by thewind during a long period of time and then continues as swell also afterthe wind has subsided. This results in slow variations in the averageenergy content of the waves, which gives system advantages when waveenergy converters are connected to the general electric powerdistribution network.

A reason why, in spite of this potential, there are so few competitivesolutions today is that wave energy is difficult to master. The ocean isa rough environment with high material stress. In stormy weather theenergy levels can be a 100 times higher than normal. The wave motion isoscillating and with never ceasing variations in height, length and timeperiod (velocity) from wave to wave, this giving large variations in theenergy absorbed by a wave power plant. For direct driven operation, i.e.when the generator in the wave power plant is driven according to themomentary motion of the wave, this results in a low utilization of thepower plant, i.e. the so called capacity factor takes a low value. Thepower of the generator shifts between zero and a top level twice everywave period. The top level may also change very strongly from wave towave. The general electric power distribution network requiresrelatively stable levels, both in delivered power and voltage, thisresulting in that the electrical control systems for this kind of waveenergy converters must, after the generation, make the levels of thesemore even. Also, the uneven levels results in a costly over-dimensioningof the total electrical system of a wave power plant in order to obtaina proper handling of the top power levels.

To make wave power competitive a wave power plant is required that canefficiently absorb the wave energy at the same time as the motive forceon the generator is leveled, so that a higher capacity factor isobtained. Also, a low system complexity and an efficient use ofcomponents are required. The structure of the wave power plant must alsobe storm proof and have a long life-cycle, and low operational andmaintenance costs that can be achieved by a construction allowing longservice intervals and includes wearing parts that can be easilyaccessed.

Wave power technology has been developed for a long period of time butso far it has not been possible to arrive at a method or a design of awave power plant, where it has been possible to combine the necessaryproperties as described above.

A frequent method of capturing the energy of water waves is to use thevertical motion of the water. Installations that use such technology aresometimes called “point absorbers”. One way of using the vertical motionincorporates a buoy having a bottom foundation and an anchor wheel. Thebottom foundation is firmly positioned at the sea-floor and is connectedto the buoy which follows the ocean surface, i.e. the wave motions. Whenthe surface rises and thereby lifts the buoy, a motive force is created,which is converted to a rotational motion by a driveshaft connectedbetween the foundation and the buoy or by a wire or chain, which runsover an anchor wheel journalled in bearings at the buoy or in thefoundation and which at an opposite end is connected to the foundationor the buoy, respectively. The motive force increases due to theincreased motion speed of the waves when the wave height becomes higher.The rotational direction and speed of an anchor wheel, is such a wheelis used, is directly dependent on the vertical direction and motionspeed of the waves. However, this is not optimal for coupling aconventional generator to the anchor wheel to produce electric energy.

In order to make a wave power plant driving a conventional rotatinggenerator efficient, the vertical motion of the waves must be convertedinto a unidirectional rotational movement, and the rotation speed of anelectrical generator connected to the transmission must be stabilized.In a device, as described above, using a driveshaft, wire or chain,which is secured to the sea bottom or in a frame structure and whichruns along or over an anchor wheel journalled in a buoy, this problemcan be solved in the following way. When the buoy is lifted by a wave, amotive force over the anchor wheel is created. Thereupon, when the wavefalls, an anti-reverse mechanism is disengaged and the anchor wheel isreturned by a counterweight. Then, the motive driving is only activeduring the rise of the wave and ceases completely when the wave sinks,which is not satisfactory. Attempts have been made to reverse therotation direction, so that an electrical generator driven by the anchorwheel is driven by the counterweight in the same direction also when thewave sinks. It has also been attempted to reverse the rotation directionof the generator. However, changing the rotation direction of amechanical transmission or of the generator twice for every wave periodresults in heavy mechanical wear. Even though the rotation direction canmade unidirectional by the transmission, the rotation speed follows thespeed of the vertical motion, this causing that the power output fromthe generator varies according to the speed of the wave motion. Thisgives to a low capacity factor and high attenuating effects since themass of the generator all the time alternatingly be accelerated anddecelerated. In order to make the motive force and rotation speed of agenerator using a mechanical transmission multiple buoys can cooperate,a phase shift existing between the buoys. However, this only worksoptimally in the case where the buoys are evenly distributed over a waveperiod, which very seldom occurs the length and speed of the wavesalways vary. Also, the transmission system becomes more complex andhence hydraulic mechanisms are frequently used in systems of this type.However, hydraulic devices results in complex systems having largetransmission losses. A wave power plant of the type described above isdisclosed in the published French patent application 2869368, whichcomprises a floating platform or buoy. Lines run over pulleys at thebuoy, one end of the lines being attached to the bottom and the otherend carrying a counterweight. The rotation of the pulleys is transferredto generators. The rotation speed and power output from the generatorvary according to the motion of the waves. A similar wave power plant isdisclosed in U.S. Pat. No. 4,242,593, which drives a wheel or pulley inthe buoy only when it is rising. A gearbox is provided for gearing upthe rotation speed of the wheel or pulley in the buoy to make itsuitable to be used for driving a generator. In U.S. Pat. No. 5,889,336and the published Japanese patent application 11-6472 a similar waveenergy plant is disclosed including a chain which at one end is attachedto a bottom foundation end and at its other end has a counterweight. Thechain passes over a chain pulley in a buoy. The chain pulley isconnected to a generator through a directly acting transmission, whichis arranged so the generator always rotates in the same direction. Therotation speed depends on the speed of the vertical motion of the buoy.

A wave power installation of a somewhat different type is disclosed inU.S. Pat. No. 4,241,579. A driveshaft is mounted to be elevated and sunkbetween the water surface and the bottom. A number of buoys are by wiresconnected to counterweights and the lines pass around the commondriveshaft for driving only when the respective buoy. In the publishedBritish patent application 2062113 a wave energy converter is disclosedincluding a plurality of different drive mechanisms, each one of whichcomprises a buoy and a counterweight/bottom foundation/additional buoyand which act on a common driveshaft through one-way couplings. In thepublished French patent application 2339071 a buoy is used, which isconnected to one end of a chain and by the chain drives a driveshaftplaced above the water surface to rotate. The other end of the chaincarries a counterweight, which is also placed above the water surface.The connection to the driveshaft is of a unidirectional type and thedriveshaft may be driven by several such buoys through chains.

In the published International patent application WO 2005/054668 a waveenergy plant including a buoy which is attached to an end of a line isdisclosed. The other end of the line is more or less wound up around adrum placed on the bottom of the sea. The drum is connected to a returnspring and a generator and drives the generator in both the rising andsinking motion of the buoy. In the wave energy plant according to thepublished International patent application WO 03/058054 the buoy acts asan winding drum for a line, the lower end of which is connected to abottom foundation. A return spring, a gear up mechanism and a generatorare located inside the drum. The generator is driven in both the risingand sinking motion of the buoy.

SUMMARY

It is an object of the invention to provide an efficient wave energyplant.

In a wave energy plant energy from water waves in a pool of water duringparts of the motions of the water waves is absorbed for driving anelectrical generator. However, part of the absorbed energy istemporarily accumulated or stored in some suitable mechanical way fordriving the electrical generator during other parts of the motions ofthe water waves. Thereby, an equalization over time of the motive force,which drives the electrical generator, can hereby achieved. For thetemporary mechanical accumulation of energy a change of potential energycan be used, such as variations of the potential energy of a suitablebody. For example, the change of potential energy can be based onelastic forces or on gravitational forces. In the latter case a floatingbody can be used, i.e. a body having a density lower than that of water,which is located at a varying distance from the water surface and herebyindirectly uses the gravitational forces. The body used for accumulationof energy can in the same case alternatively be a counterweight, i.e. abody having a density higher than that of water, which uses thegravitational forces in a more direct way. The body may in these casesbe connected to some elongated means, such as a line, wire or chain,which in the case where it is flexible can be more or less wound arounda counterweight drum. The counterweight drum can be journalled at a buoyor at a stationary rack or frame placed on or attached the bottom of apool of water. The counterweight drum can in one case be mechanicallyconnected to a rotating part of an electrical generator and the weightor buoyancy of the body is used for continuously driving thecounterweight drum to rotate in an opposite relative rotationaldirection compared to the rotational direction of a driveshaft, which isconnected to another elongated means, also here for example a line, wireor chain.

The driveshaft is mechanically arranged for a unidirectional rotationonly, driven for example by the rising or sinking motions of a watersurface or more particularly by alternatingly rising and sinkingmovements and/or alternating tilting, back and forth movements of abuoy, i.e. a body having a density lower than that of water, which isfloating at the water surface, or alternatively by some other form ofoscillatory movement or combination of oscillatory movements in thewaves or in the water. The electrical generator is in the abovementioned cases mechanically connected in a transmission path betweenthe driveshaft and the counterweight drum. The electromagnetic couplingbetween the parts in the electrical generator over the air gap of thegenerator gives a limited torque in relation to the rotation speed ofthe generator, the mechanical torque provided by the counterweight drumand the electrical load of the generator. When the driveshaft isrotating faster than the rotational speed in the generator, thecounterweight drum is rotated in a first rotational direction, thiscausing the counterweight to be hoisted up, thereby accumulatingpotential energy. When the driveshaft is rotating slower than therotation speed in the generator or is still-standing still, thecounterweight drum rotates in a second rotational direction, thiscausing the counterweight to be lowered, thereby releasing potentialenergy.

As an energy accumulation device, which uses elastic forces, an elasticor resilient mechanism may be used, in which the energy is accumulatedas a tension in a spring or generally as elastic energy. Such an elasticdevice may in a different case comprise a container for accumulation ofenergy as a gas pressure. The container may then be connected to acombined compressor or gas pump and a pneumatic motor such as a scrollpump. This device may have one moving part directly connected to one ofthe parts of the generator.

In such a wave energy plant it is possible achieve, using an energyaccumulation device, also called energy storing device, and suitablecouplings, an equalization of the kinetic energy of the water waves inan efficient way, so that the generator can be driven to continuouslygenerate electricity at a relatively even level.

Generally, a wave energy plant or in its most common form a power plantusing movements, such as more or less periodic motions, of the water ofa pool of water, can comprise:

-   A buoy or other device, which is arranged at or in the pool of water    to be made, in some way, to move by movements of the water in the    pool of water. Then, the buoy or the other device is constructed and    placed so that it itself, because of movements in the water, obtains    movements, which alternate between a movements in one direction and    a movement in another direction that is different from the first    direction. The movements in the water can comprise wave movements in    the water or at the surface of the water, alternating movements,    i.e. alternating back and forth movements in the water or at the    surface of the water or generally movements alternating between a    movement in one direction and a movement in another direction in the    water of the pool of water. In the case of a buoy, floating at the    surface of the water in the pool of water, this can mean that the    buoy, at the up and down movements of the water surface,    alternatingly rises and sinks and/or alternately rocks or tilts back    and forth. In general then, the buoy has an average density lower    than that of water. The other device arranged at or in the pool of    water may for example comprise a body having the same density as or    a higher density than that of water, which is designed to follow the    movements of the water, or a device that is being alternately    compressed and expanded due to pressure differences in the water    which occur when water waves pass.-   A driveshaft, which is rotationally journalled at some part of the    wave power plant. In different designs, it can be journalled at the    buoy or at the other device. Alternatively it can be journalled for    rotation at a device that is rigidly attached to the bottom of the    pool of water, or generally to some device arranged to counteract    the movements of the water in the pool of water, such as a body    having a relatively large mass or weight.-   A first elongated means, which both is connected to a device    arranged to counteract the movements of the water in the pool of    water, for example a fixed point at the bottom of the pool of water    or a body having a relatively large mass or weight, or to the buoy,    respectively, depending on the place where the driveshaft is    mounted, and is connected to the driveshaft. The first elongated    means may be a flexible means, such as a line, wire or chain, but it    can also be stiff, in that case for example comprising a rack    gearing segment.-   An electric generator connected to the driveshaft and comprising two    parts that are rotatable in relation to each other, a first part and    a second part, often called rotor and stator, respectively. An air    gap exists between the two rotatable parts.-   An accumulation device for temporary mechanical storage of energy as    described above.

The buoy or the similar device is arranged and the buoy or the otherdevice, the first elongated means, the device arranged to counteract thewave movements, the driveshaft and the energy accumulation device areconnected to each other, so that the connection between the firstelongated means and the driveshaft makes the driveshaft rotate,substantially for first movements of the water surface or for firstmovements of the buoy or the similar device, in only one direction,thereby driving said two part of the electric generator to rotate inrelation to each other in a first direction and generate electricity andat the same time also supply energy to the accumulation device. Thus,energy from the rotation of the driveshaft is hereby partly converted toelectric energy, which is delivered from the electric generator, partlyto energy which is stored in the energy accumulation device. The firstmovements can for a buoy be the movements into which the buoy is set byeither one of the up- or down-going movements of the water surface.

The energy accumulating device is arranged to drive, for substantiallysecond movements, that are substantially different from the firstmovements, of the buoy or the similar device, said two parts of theelectric generator to rotate in the same first rotation direction inrelation to each drives said two parts of the electrical generator torotate in relation to each other. The second movements can for a buoy bethose movements, into which the buoy is set by second of the up and downgoing movements and thus are substantially different from said eitherone of the up and down going movements of the water surface.

The first movements of the buoy or the other body can take place in adirection, which is mainly the opposite the direction, in which thesecond movements of the buoy or the other device are made. Thus, thefirst movements can take place in a forward direction whereas the secondmovements take place in a backward direction, either as a translationmovements, for example up or down, or as a rotational motion, i.e.angularly, or as a combined translation and rotational movement.

The driveshaft may be mechanically connected, for example via amechanical gear, to the first part of the electric generator. Anelectromagnetic coupling exists in a conventional way over the air gapbetween the first and second parts of the electric generator at leastwhen these parts are moving in relation to each other. The energyaccumulation device may in one special embodiment be mechanicallyconnected to the second part of the electric generator.

The connection of the energy accumulation device to the driveshaft viathe electromagnetic coupling over the air gap between the first andsecond parts of the electric generator gives a motive force, whichcounteracts to the rotation of the driveshaft when the driveshaft isrotating, by the connection between the first elongated means and thedriveshaft, and thereby is driving the first part of the electricgenerator. Then, in the above mentioned special embodiment, the secondpart of the electric generator can rotate in a first direction due tothe coupling to the drive shaft through the electromagnetic couplingover the air gap and the first part of the electric generator, when themotive force which is acting on the driveshaft through the couplingbetween the first elongated means and the driveshaft exceeds thecounteracting motive force, energy being accumulated in the energyaccumulation device due the mechanical coupling thereof to the secondpart of the electric generator. At the same time, the first and secondparts of the electric generator are rotating in the same first directionin relation to each other. Furthermore, the second part of the electricgenerator is driven by the energy accumulation device to rotate in thesame first direction substantially when the motive force, which acts onthe driveshaft through the coupling between the first elongated meansand the driveshaft, does not exceed the counteracting motive force.Hereby, the first and second parts of the electric generator are made tocontinue to rotate in the same first direction in relation to each otheralso in this case.

As has been mentioned above, a mechanical gear may be arranged forcoupling the driveshaft to the first part of the electric generator. Thedriveshaft is then suitably connected to an input side of the mechanicalgear and the first part of the electric generator is mechanicallyconnected to a first output side of the mechanical gear. In this case,the second part of the electric generator can be rigidly attached to thebuoy, if the energy accumulation device is connected to a second outputside that is different from the first output side of the mechanicalgear. A mechanical gear can generally be regarded to comprise one inputside having an input shaft and two output sides, where one of the outputsides comprises an output shaft and another output side comprises ahousing or enclosure of the mechanical gear, also see the discussionbelow of only the transmission included in the wave energy plant. Forexample a planetary gear, the input side may comprise a shaft connectedto the planet gear carrier and the two output sides correspond to shaftsconnected to the sun gear and ring gear, which may be connected to asecond shaft or the housing of the planetary gear.

In the case including a buoy, the buoy can comprise a space whichfunctions as an air pocket and in which at least the main part of thedriveshaft is mounted as well as other rotating parts, such as windingdrums, in the case where such are provided and couplings between them.Such an air pocket can be a space filled with air, which at its bottomis delimited by a water surface and the other sides of which aredifferent surfaces of the buoy. Then, the air pocket may be formed by arecess in the bottom surface of the buoy.

The energy accumulation device can in one embodiment comprise acounterweight, arranged as a lead, to also move upwards for said firstmovements of the buoy or the other device, thereby increasing itspotential energy. The coupling of the buoy or the other device, thefirst elongated means, the driveshaft and the counterweight to eachother is then suitably arranged so that the counterweight movesdownwards, for said second one of the movements of the buoy or the otherdevice, thereby driving the parts of the electric generator to rotate inrelation to each other in the first rotational direction. In the case ofa buoy, this can for example mean that, for the first movements, whenthe buoy e.g. is moving upwards, the counterweight is also movingupwards a distance, which is greater than the vertical distance in whichthe buoy then vertically moves.

The energy accumulation device can in the same embodiments comprise acounterweight drum which is rotationally mounted to the driveshaft and asecond elongated means for coupling movements of the counterweight tomake the counterweight drum rotate. The second elongated means can beflexible or can be a flexible means such as a line, wire or chain, whichat a lower end is attached to the counterweight and at its upper end ismore or less wound around the counterweight drum. Furthermore, thedriveshaft is connected to drive the first part of the electricalgenerator to rotate and the counterweight drum can in a first case becoupled to rotate the second part of the electric generator, so that theelectric generator generates electric current when its second part isrotated in relation to its first part and at the same time gives atorque counteracting this rotation. Hereby, the first and second partsof the electric generator can be made to always rotate always in thesame first direction in relation to each other.

In a second case a mechanical gear can be connected between thedriveshaft and the first part of the electrical generator. In this casethe driveshaft is connected to an input side of the mechanical gear, thesecond part of the electric generator is rigidly attached to the buoy orthe other device and the counterweight drum is mechanically coupled to asecond output going side different from the first output side of themechanical gear. The driveshaft can hereby, for said first movements ofthe buoy or the other device, provide motive forces on both of theoutput sides of the gear, in order to rotate the first part of theelectric generator and to rotate the counterweight drum to elevate thecounterweight in relation to the driveshaft. The counterweight drum can,for said second movements of the buoy or the other device, provide amotive force, through its coupling to the second output side of thegearbox, in order to rotate the first part of the electric generator.

Furthermore, in the case including a counterweight and a counterweightdrum, an electric cable for the electric connection of the generator canbe provided which extends from the generator to the counterweight drumand is partly wound around it, which therefrom extends to a nonfloatable part which is slidable along the first elongated means and towhich it is rigidly connected, so that the sliding part can bemaintained at a constant distance beneath the counterweight, and whichelectric cable extends from the slidable part up to the water surface tobe further connected to an electric load. This may allow the wave energyconverter to turn in the horizontal plane, such as when the direction ofthe water waves changes, without causing the electric cable to beentangled with the first elongated means.

An anchor drum can be mounted for unidirectional rotation around thedriveshaft and further be coupled to the first oblong organ to make theanchor drum rotate for the first ones of the movements of the buoy orthe other device, and thereby also making the driveshaft rotate. Thefirst elongated means can be flexible, i.e. be a flexible means such asa line, wire or chain, which at one end is more or less wound around theanchor drum. A mechanism can be provided for rotating, for the secondmovements of the buoy or the other device, the anchor drum so that theflexible organ is kept in a tensioned state. Hereby, in can also becounteracted that the wave energy plant is moved away along the surfaceof the water. The mechanism can for example comprise a mechanicalcoupling between the energy accumulation device and the anchor drum orcomprise an electric motor.

The bearing for the anchor drum, which only allows a unidirectionalrotation around the driveshaft, at the same time allows the anchor drum,when rotating in the opposite direction, to drive the driveshaft torotate in the opposite direction, which is the above said only onedirection. This bearing can comprise a coupling for limiting ordisengaging the motive force with which the anchor drum then acts on thedriveshaft.

A control system for controlling the electrical load of the electricgenerator can be provided that is arranged to adapt the rotational speedbetween the first and the second parts of the electric generator. In thecase where the energy accumulation device comprises a counterweight or afloating body, control of the electrical load can also be used for adaptthe vertical speed of the counterweight or of the floating body,respectively, whereby it also becomes possible for the counterweight orthe floating body, respectively, to only move within an adapted orsuitable vertical range. The control system can also be arranged tocompensate for variations in the torque, which is caused by the inertiaof the mass of the counterweight or the floating body, respectively, byadjustment of the rotation speed between first and the second parts ofthe electric generator. Hereby it can be achieved that the electricgenerator is capable of supplying a continuous, even power.

The wave energy converter may have one or more of the followingcharacteristics and advantages:

-   1. Accumulation of energy according to the description above can be    used for equalizing the energy of the water waves and thereby    generate electricity at an even level, which gives a high capacity    factor of the generator and associated power electronic circuits and    connections, and a low complexity of the electric power system.-   2. Excess energy from large waves can be accumulated and used over    time to compensate for shortage in smaller waves, which contributes    to the high capacity factor.-   3. Absorption of energy from the water waves can be limited while    full power can be maintained even during very heavy wave conditions.    This contributes to the high capacity factor, but it also works as a    very simple and efficient storm protection system where the wave    energy plant all the time works in harmony with the waves, only    absorbing the amount of energy that it has a capacity to convert.-   4. The power output of the generator can be controlled by the fact    that the rotation speed of the generator can be adapted to the    average rotation speed of the driveshaft. This brings about that the    wave energy plant can deliver an even power level in relation to the    current wave climate.-   5. The wave energy plant is highly scalable and its capacity and    pattern producing electric power can be optimized for specific wave    climates for the highest cost efficiency.-   6. The wave energy plant has a completely mechanical transmission    having a high efficiency, which in simple way converts the    oscillating wave movements into a unidirectional rotation, well    adapted to a standard electric generator having a rotating rotor.-   7. The construction can for example mainly be made from concrete, a    cheap material which is well tested for ocean environment.-   8. An electronically adjustable sliding clutch may be used, which is    arranged to influence the winding of a line between a bottom    foundation and the buoy and which also makes it possible to adjust    the force which is needed to maintain the horizontal position of the    wave energy plant. Such a sliding clutch may replace and enhance the    function of a counterweight, here called a lead, which is often used    in similar constructions.

9. An anchor drum, which is mechanically connected to the driveshaft,can be used for more or less winding the second elongated means,according to the wave movements. Several revolutions of the anchor linecan be wound around the anchor drum and hence it has no technicallimitations for wave heights that the installation can handle. The buoyfollows the surface of the water in a harmonic way for all wave sizeswithout reaching any end position, which contributes to the fact thatthe wave energy plant can very efficiently absorb wave energy, in spiteof varying wave heights and at the same time the strain on theconstruction during storm conditions is minimized.

-   10. Mechanical couplings may be provided, so that if the electrical    generator is supplied with electric energy from an external source    and acts as an electrical motor, the anchor drum can be controlled    to move to perform a controlled winding of the line. This can confer    to the wave energy plant the property that it can be assembled on    shore before it is towed to the installation site thereof.-   11. The installation can be done with a minimum of manual    assistance. It is mainly only an electric cable that has to be    manually connected, which can be done at the surface of the water    from a boat. A bottom foundation, which is connected to the second    elongated means, and the counterweight are attached to the buoy    during transport to the installation site and then they can be    released by control of mechanic couplings/locking devices.-   12. The wave energy converter can easily be designed to be suitable    for different installation depths.-   13. A gearbox can be used to increase the rotation speed of the    electrical generator, this allowing the use of a smaller and more    resource efficient high speed generator. Such a gearbox can also    make it possible to permanently fix the second part of the electric    generator, the stator, to the buoy, by connecting the gearbox to the    counterweight drum, which can simplify the electrical connection and    encapsulation of the generator and reduce the rotating mass in the    construction.

Generally, as described above, a method of extracting electric energyfrom more or less periodic movement of a body, such as repeated upwardand downward movements and/or tilting movements in two oppositedirections can comprise the following steps.

-   For first movements of the body, these movements can drive two parts    of an electric generator to rotate in relation to each other in a    first direction and thereby generate electric current and at the    same time provide mechanical energy to an energy accumulation    device.-   For second movements of the body, which are substantially different    from the first movements, the energy accumulation device can drive    the two parts of the electrical generator to rotate in the same    first direction in relation to each other and thereby generate    electric current having the same polarity as during the first    movements of the body.

The transmission used in the wave energy converter as described abovecan independently be used in other cases of power generation, where adriveshaft is driven intermittently, with changing directions and/orwith varying speeds and/or torques. Generally, the transmission thencomprises a driveshaft that is arranged to be driven and that by somesuitable device, if required, always can be made to rotate in onerotational direction. Furthermore, an electrical generator coupled todriveshaft is provided, which generator comprises two parts that canrotate in relation to each other, and an energy accumulation device. Thedriveshaft drives the two parts of the generator to rotate in relationto each other in a first direction and thereby generate electriccurrent. The energy accumulation device is coupled with the driveshaftand the electric generator, so that the driveshaft by its rotation canalso supply energy to the energy accumulation device and so that theenergy accumulation device can later deliver its stored or accumulatedenergy to cooperate in driving the parts of the generator to rotate inthe same first direction in relation to each other. Thereby, electriccurrent can be generated having the same polarity, when the rotationalspeed and/or the torque of the driveshaft is/are insufficient to drivethe parts of the generator to rotate at a maintained rotational speed.

In the transmission, the driveshaft can be mechanically connected to thefirst one of the parts of the electrical generator. In the generatorthere is, as conventionally, an electromagnetic coupling over an air gapbetween the first and the second part, at least during their movementsin relation to each other, which the coupling gives some torque betweenthe two parts. The energy accumulation device can in a first case bemechanically coupled to the second part included in the electricalgenerator.

Furthermore, in the transmission a gearbox, e.g. a planetary gearbox,can as described above be connected between the driveshaft and thegenerator, so that the driveshaft is mechanically connected to the inputside of the gearbox or generally to a first rotational part of thegearbox. An output side of the gearbox or generally a second rotationalpart of the gearbox is then arranged to be driven from the outside torotate with a varying rotational speed and/or torque in one rotationaldirection. One of the two parts of the electrical generator ismechanically coupled to another output side of the gearbox, generally athird rotational part of the gearbox, and the energy accumulation deviceis mechanically coupled to the second part of the generator. The firstand second rotational parts of the gearbox can then cooperate to forexample drive the third rotational part of the gearbox to rotate with arotational speed higher than the rotational speeds that each of theparts by itself can achieve when the other of these parts stands stillor is not driven.

The gearbox should in any case have the following functions:

-   When the first rotational part is driven from the outside, the    second and the third rotational parts are also made to rotate.-   When the first rotational part is not rotating, the third rotational    part can drive the second rotational part to rotate.

The first, second and third rotational parts can also be arranged torotate around the same geometric rotational axis, i.e. be coaxiallymounted.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe methods, processes, instrumentalities and combinations particularlypointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

While the novel features of the invention are set forth withparticularly in the appended claims, a complete understanding of theinvention, both as to organization and content, and of the above andother features thereof may be gained from and the invention will bebetter appreciated from a consideration of the following detaileddescription of non-limiting embodiments presented hereinbelow withreference to the accompanying drawings, in which:

FIG. 1 is a schematic image of a wave power installation comprising fourseparate wave energy plants,

FIG. 2 a is a side view of a wave energy converter including acounterweight,

FIG. 2 b is a front view of the wave energy plant of FIG. 2 a,

FIG. 2 c is a sectional view of a wave energy plant having analternative suspension of a power train,

FIG. 2 d is a different sectional view of the wave energy plant of FIG.2 c,

FIG. 2 e is a view from underneath only comprising a buoy includingsteering fins, an anchor drum and a counterweight drum according to FIG.2 c,

FIG. 2 f is a view from underneath of the wave energy plant of FIG. 2 cwhich also shows an air pump,

FIG. 2 g is a top view of a power train for a wave energy convertermounted in a frame,

FIG. 3 a is a front view of a power train including winding drums, adriveshaft and a generator in the wave energy plant of FIG. 2 a,

FIG. 3 b is a view similar to FIG. 3 a in which parts of a generator areschematically shown and in which a spiral spring is used as an energyaccumulation device,

FIG. 3 c is a front view of winding drums having specially designedwinding surfaces,

FIG. 3 d is a schematic of a power train comprising a generator having astationary stator,

FIG. 3 e is a front view of a wave energy plant including a frame forinterconnecting two counterweights,

FIG. 3 f is a top view of the frame of FIG. 3 e for interconnecting twocounterweights,

FIG. 4 is a front view of the wave energy plant of FIG. 2 a having aspecially designed electric cable connection,

FIG. 5 a is a detail view of an anchor drum and its couplings located atthe shaft,

FIG. 5 b is a view similar to FIG. 5 a for a different design of thecouplings,

FIG. 5 c is a schematic of an anchor drum having couplings designed inyet another alternative way,

FIG. 5 d is a diagram illustrating a control rule for engagement anddisengagement of a slipper clutch,

FIG. 5 e is a schematic view of a claw clutch in an engaged state,

FIG. 5 f is a schematic view of a claw clutch in a disengaged state,

FIG. 6 is a detail view of a mechanical coupling for return feed betweenan anchor drum and a counterweight drum,

FIG. 7 a is a front view of an alternatively designed wave energy plantincluding counterweights,

FIG. 7 b is a front view of an alternatively designed wave energyconverter including buoys instead of counterweights,

FIG. 7 c is a front view of yet another alternatively designed waveenergy converter including counterweights located above the watersurface,

FIG. 7 d is a front view of a wave energy plant having an alternativedriving operation of the driveshaft by cooperation with a weightsuspended in an elastic means,

FIG. 8 a is a front view of a combined wind and wave energy plant,

FIG. 8 b is a side view of the combined wind and wave energy plant ofFIG. 8 a,

FIG. 8 c is a detail view of a power train comprised in the combinedwind and wave energy plant of FIG. 8 b,

FIG. 8 d is a front view of a wind power plant, in which a transmissionof the same kind is used,

FIG. 8 e is a side view of the wind power plant of FIG. 8 d,

FIG. 8 f is a detail view of the wind power plant of FIG. 8 e having apneumatic energy accumulation device,

FIG. 9 a is a front view of a wave energy plant having an energyaccumulation device designed as an elastic means,

FIG. 9 b shows an alternative connection of the elastic means of FIG. 9a,

FIG. 10 a is a schematic front view of a wave energy plant including anenergy accumulation device and a return feed mechanism,

FIG. 10 b is a view similar to FIG. 10 a of a wave energy plantconverter using the torque which is transferred over the air gap of agenerator to obtain energy accumulation,

FIG. 11 a is a schematic of a previously known device for driving agenerator in a wave energy plant,

FIG. 11 b is an schematic similar to FIG. 11 a but of a differentlydesigned device for driving a generator having a stator that also isrotating,

FIG. 11 c is a view from a different side of the device of FIG. 11 b,

FIG. 11 d is a schematic similar to FIG. 11 b of a device arranged in adifferent way design for driving a generator having a stationary stator,

FIG. 11 e is a view from a different side of the device of FIG. 11 d,

FIGS. 12 a and 12 b are views from two sides, illustrating theconstruction and function of a planetary gear,

FIGS. 12 c and 12 d are schematic views, illustrating the constructionof a variable mechanical gear (CVT/CVET),

FIG. 12 e is a view of a planetary gear and a variable gear which arecoupled with a generator in a power train,

FIG. 13 a is a front view of a power train having steering rollers forthe guidance of lines,

FIG. 13 b is a side view of the power train of FIG. 13 a,

FIG. 13 c is a bottom view of the power train of FIG. 13 a,

FIG. 14 is a bottom view of a power train including only one generatormounted in a buoy,

FIG. 15 a is a front view of a wave energy plant having an alternativedesign of a power train including only one generator, the stator ofwhich rotates together with the counterweight drum, one counterweightand an alternative guide mechanism for an anchor line,

FIG. 15 b is a side view of the wave energy plant of to FIG. 15 a,

FIG. 15 c is a front view of a wave energy plant of FIG. 15 a having adifferent type of divided anchor line,

FIG. 15 d is a side view of the wave energy plant of FIG. 15 c,

FIG. 15 e is a bottom view of the power train of the wave energyconverter of FIG. 15 a,

FIG. 15 f is a bottom view similar to FIG. 15 e but including a powertrain in which the stator of the generator is rigidly attached to thebuoy,

FIG. 15 g is a bottom view of a power train similar to FIG. 15 f, inwhich the mechanical components are encapsulated to a larger extent,

FIG. 15 h is a front view of the power train of FIG. 15 g,

FIG. 15 i is a view similar to FIG. 15 g, in which a return feedmechanism in the power train is driven by an electric motor,

FIG. 16 a is a diagram illustrating a control rule for compensating forvarying accelerations and decelerations of the counterweight using theload of the generator,

FIG. 16 b is a diagram illustrating a control rule for compensating forvarying accelerations and decelerations of the counterweight using aCVT, and

FIG. 16 c is a diagram illustrating a control rule for compensating forvarying accelerations and decelerations of the counterweight using thesliding clutch of the return feed mechanism.

DETAILED DESCRIPTION

In FIG. 1, a wave power installation is shown for extraction of energyfrom the movements of waves at a water surface 6 of a pool of water,e.g. movements of water in a ocean. The wave power installationcomprises one or more wave energy plants 1, each including a buoy or afloating body 3, which is located at the water surface, e.g. floatingthereon, and which to a higher or lower degree follows the movements ofthe waves. In the upwards and downwards movements of the water surface 6the buoy is made to alternating raise or sink and/or alternating tiltback and forth. Thereby a motive force can be created, in the case shownin relation to the bottom 8 of the water pool, such as a part rigidlyattached to the bottom, e.g. a bottom foundation 5, which can have amass large enough to keep it steadily on the bottom. If required, thebottom foundation can of course be attached to the bottom in some wayand it may then comprise a simple fastening device having a low mass,not shown. As can be better seen in FIGS. 2 a and 2 b the buoy 3 and thebottom foundation—alternatively the bottom fastening device—areconnected to each other by an anchor line 7, e.g. a steel wire. Themotive force can as an alternative be created in relation to some kindof movable object such as to a weight suspended in the buoy, see FIG. 7d.

In the shown embodiment the anchor line 7 is at one end attached to thefoundation 5 and is at its opposite end attached to a power train 2 andmore or less wound around a first winding drum, an anchor drum 9,included in the power train, the winding drum being mounted to rotateabout a driveshaft 11. The driveshaft 11 is in a suitable way journalledat the buoy 3. As shown in FIGS. 2 a and 2 b the buoy can at its bottomside comprise downwards protruding stays 13, which can be said toconstitute a frame and at which the driveshaft 11 is journalled, e.g. atits two ends. On the driveshaft, in the embodiment shown in thesefigures, there is also a second winding drum, a counterweight drum 15,on which a line 17 is partly wound at its upper end. The counterweightline 7 carries at its lower end a counterweight 19. The cylindricalsurface of the counterweight drum, on which the line for thecounterweight is wound, has in the shown embodiment a diameter that islarger than that of the cylindrical surface of the anchor drum 9, onwhich the anchor line 7 from the bottom foundation 5 is wound. The firstmentioned diameter can e.g. be considerably larger than the latter one,such as a relation in the magnitude of order of 2:1 to 3:1, but does nothave to. The winding drums can also have the same diameter whensuitable.

Instead of having the power train 2 mounted under the buoy 3, as shownin FIGS. 2 a and 2 b, the power train can be mounted in a recess in thebuoy, a power train room 20, as shown in FIGS. 2 c, 2 d and 2 e. Then,the driveshaft 11 can be mounted in a substantially central position inthe buoy. The stays 13 can be attached to walls of the power train room20.

Thus, the anchor line 7 and the counterweight 19 are not directlyconnected to each other as in earlier known constructions. In theearlier known constructions, see the principle picture of FIG. 11 a,half the motive force of the buoy 3 is accumulated in the rise of thewave by while the anchor line 7 running over the anchor drum 9′, so thata generator 21 for generating electric current can be driven also whenthe wave thereafter sinks. In the latter case, the generator is eitherdriven in a reverse direction or the rotation movement is rectified by amechanical or hydraulic transmission solution, not shown. However, inboth cases the generator 21 remains to be direct driven according to themomentary vertical movement of the wave.

As appears from FIGS. 11 b and 11 c the generator can instead beconnected to be driven between the counterweight 19 and the anchor drum9, so that e.g. a first part of the generator, not shown in thesefigures, typically corresponding the inner rotating part, the rotor, ofa conventionally mounted generator, on one side of the air gap of thegenerator, not shown, is mechanically connected to the anchor drum and asecond part of the generator, not shown in these figures, typicallycorresponding to the outer stationary part of the generator, the stator,in a conventionally mounted generator, on the other side of the air gap,is mechanically connected to the movements of the counterweight, so thatthis part can also rotate. Hereby the generator 21 can be driven fromtwo sides with a maintained relative rotational direction between itsfirst part and its second part. When the wave and the buoy 3 raises, thedriveshaft 11 is turned forwards by the anchor line 7, which runs aroundthe driveshaft via the anchor drum 9 and which at its other end isanchored to the bottom 8, e.g. to a foundation 5. The counterweight 19is used to create a resilient resisting force and thereby gives an eventorque between the counterweight drum 15 and the driveshaft 11, which inthat way drives the first part and second part of the generator inrelation to each other. It is also possible to use other methods toachieve such a driving operation, e.g. gas pressure or a spring forproviding a constant force, as will be described below.

In FIGS. 11 a, 11 b, and 11 c the arrows 111 show absorption of waveenergy. The absorption level varies according to the momentary movementand movement direction of the wave. When the driveshaft 11 is turnedforwards by the anchor drum 9, also the generator 21 follows therotation, so that the counterweight line 17 starts to be wound aroundthe counter weight drum 15, which can be a part of or be rigidlyattached to the second part of the generator, see the arrows 113, and sothat the counterweight is moved upwards. Hereby, potential energy isstored in the counterweight at the same time as a torque appears overthe generator (torque=weight of the counterweight*acceleration ofgravity (i.e. the gravitational force acting on thecounterweight)*radius of the counterweight drum). The torque makes thesecond part of the generator start rotating in relation to the firstpart, which is mechanically connected to the driveshaft 11, so that thecounterweight line 17 starts to unwind from the counterweight drum 15,and hereby potential energy accumulated in the counterweight 19 isconverted to electricity, see the arrows 115. The faster the generatorparts rotate in relation to each other, the more electric power isgenerated, and then also a higher counteracting force is obtained in thegenerator 21, i.e. the electromagnetic coupling between the two parts ofthe generator becomes stronger. When the counterweight 19 reaches acertain velocity, the pulling force from the counterweight becomes equalto the counteracting force in the generator, this resulting in that therotation speed of the generator and the power output from the generatoris stabilized in an equilibrium state.

This way of connecting and driving the generator 21 can give greatadvantages, since the generator can be used much more efficientlycompared to what have been earlier possible. The same relativerotational direction between the generator parts is maintained all thetime and the generated electric power is kept at a substantially evenlevel, which requires a minimum of subsequent electric treatment of theelectrical voltage generated by the generator. The arrangement of thegenerator can also give advantages from a storm safety point of view,since the motive force over the generator and transmission is limited.

The design of the transmission unit 2 and the function thereof will nowbe described in more detail with reference in particular to FIGS. 2 a, 2b and 3 a.

During the movements of the waves the distance between the buoy 3 andthe bottom foundation/bottom fastening device varies. The anchor drum 9is turned, due to the coupling with the anchor line 7, in a firstdirection when the water surface 6 rises, and is then locked to thedriveshaft 11, which thereby is rotated by the anchor drum. When thewater surface at the buoy sinks, the driveshaft is locked from rotatingbackwards in the opposite direction by anti-reverse mechanisms 53 in theshaft stays 13, see FIGS. 5 a and 5 b. To be capable of turning theanchor drum backwards, in a second, opposite direction, and to keep theanchor line in a tensed state when the water level 6 at the buoy 3sinks, a return feed mechanism of some kind sort is required as will bedescribed below. The driveshaft 11 is in turn connected to the generator21. The coupling between the driveshaft and the generator can be fixedor it can as illustrated comprise a mechanical gear 23, which e.g. has afixed teeth relation or fixed gear ratio, and which gears up therotation speed of the generator. Hereby one of the parts of generatorthat are rotatable in relation to each other, here for the sake ofsimplicity called rotor and stator, e.g. an inner generator rotor 21′,compare FIG. 3 a, to rotate in the first direction. The other rotatablepart of the generator, e.g. an outer stator 21″ is rigidly mounted tothe counterweight drum 15. The generator parts are separated by an airgap 21′″.

Due to the winding of the counterweight line 17 around the counterweightdrum 15 during the forward feeding of the driveshaft 11, a relativelyconstant motive force or a relatively constant torque acting on thedriveshaft 11 is achieved, which through the connection between therotor 21′ and the stator 21″ of the generator 21 drives the generator torotate and generate electric current. When the torque from the anchordrum 9 exceeds the counteracting torque, that is derived from theelectromagnetic coupling over the air gap between the rotor and thestator of the generator, when these parts are rotating in relation toeach other, more of the counterweight line 17 is wound around thecounterweight drum 15 and the excess energy, to which this higher torquecorresponds, is accordingly accumulated the hoistening of thecounterweight 19. Thereafter, when the buoy 3 starts to rise with adecreasing speed, to thereupon sink when the water surface 6 sinks, alsothe rotational speed of the driveshaft 11 and the rotor 21′ in the firstrotational direction is also reduced. When the torque from the anchordrum 9 becomes lower than the counteracting torque in the generator 21according to the discussion above, the counterweight line 17 starts tounwind from the counterweight drum at an increasing speed, until of thedriveshaft is blocked from rotating in the reverse direction by ananti-reverse mechanism 53 in the driveshaft stay 13, see FIGS. 5 a and 5b, and the speed of the backward rotation of the counterweight drum isstabilized by the equilibrium state between the generator and thecounterweight 19. The potential energy accumulated in the counterweighthence continues to drive the generator 21 also in this phase, with acorrespondingly even torque as in the previous phase.

As has been mentioned above, the wave energy is absorbed from thetraction force that arises between the buoy 3 and the bottomfoundation/bottom fastening device 3 during the rise of the wave. Thebuoy 3 follows the movements of the wave and thereby moves thedriveshaft 11, on which the anchor drum 9 is mounted, upwards inrelation to the bottom foundation. A rotational movement arises whichdrives the transmission. The vertical movement of the wave is convertedinto a rotational movement, the speed of which can then be geared up tobe suitable for driving the generator 21. It is the speed of thevertical movement of the wave that determines the amount of energy thatcan be extracted. The bigger wave, the faster vertical movement and themore energy can be absorbed. Different from the energy in the wave, thevertical speed of the movement does not increase with the square of thewave height, but follows a more linear pattern. But the larger the waveis, the less impact has the attenuating effect of the buoy 3, thisresulting in that the vertical movement and the motive force of the buoyrapidly increase when the wave height increases from a low level tolevel out towards the linear pattern the higher the wave becomes.

The anchor drum 9 is in a suitable way mechanically connected to thedrive shaft 11. Such a mechanical coupling can include the following twofunctions.

-   1. During the rise of the wave the anchor drum 9 shall hook on to    the drive shaft 11, so that the driveshaft is rotated together with    the rotational movement of the anchor drum. When the wave sinks, it    shall be possible to disengage the anchor drum, so that the anchor    drum can be rotated in the reverse direction. Furthermore, the    driveshaft 11 shall be blocked from changing its rotational    direction when the wave sinks. The drive shaft is in this manner fed    forward by the anchor drum in the same rotational direction every    time the wave rises and the motive force, and thereby rectifies the    motive force absorbed from the wave motions. This makes it possible    to drive the generator in a single rotational direction.-   2. The absorption of wave energy can be limited by the use of a    sliding clutch 55, which consequently can word as an overload    protection, see FIGS. 5 a, 5 b and 5 c. Such a sliding clutch also    makes it possible to completely disengage the absorption of energy    from the movements of the waves, by letting the anchor drum 9 slide    against the driveshaft 11 during the rise of the wave, when the    accumulation level reaches its upper limit, i.e. when it is not    possible to wind more of the counterweight line 17 around the    counterweight drum 15 without risking that the counterweight 19    comes to close to and damages the counterweight drum 15 and the buoy    3. The sliding clutch can also be used to limit the torque to which    the transmission is submitted. When the wave sinks, the buoy 3 and    the counterweight 19 will be retarded, which gives an increased    g-force and hence an increased torque in the transmission. When the    wave turns and rises again, the g-force will increase further by the    anchor drum 9 starting to be turned forward and lifting the    counterweight in relation to the buoy at the same time as the buoy    is lifted by the wave. For a too high load the sliding clutch slides    and thereby somewhat reduces the acceleration, which in turn also    reduces the torque to which the transmission is submitted.

A mechanical coupling between the anchor drum 9 and the driveshaft 11,which provides these functions, can be designed in different ways. Sucha coupling can comprise one or more anti-reverse mechanisms and asliding clutch as will be described below.

Thus a freewheel mechanism or an anti-reverse mechanism 51, see FIG. 5a, for the coupling of the driveshaft 11 to the anchor drum can beprovided, which is herein called the anti-reverse mechanism of theanchor drum. In this case, the driveshaft passes through the anchor drumundivided. The anti-reverse mechanism 51 of the anchor drum can bedesigned like a one way bearing, which is mounted around the driveshaft.When the buoy 3 rises, the anchor drum 9 and the driveshaft 11 isturned, as above, in the first rotational direction, by way of theanchor drum hooking on to the driveshaft with the use of this returnblocking mechanism 51. When the buoy 3 sinks, the return blockingmechanism in the anchor drum 9 is released and the anchor drum 9 can bereversed, rotated in the opposite rotational direction, to wind up theanchor line 7, such as will be described below, meanwhile the driveshaft11 is blocked from rotating in the opposite rotational direction byanother return blocking mechanism 53, which is acting between thedriveshaft and the stay 13 and which is here called the shaft stayreturn blocking mechanism 53. This return blocking mechanism can bearranged at or in the stay bearing 54 for the driveshaft 11. In this waythe driveshaft is always turned in the first rotation direction everytime the buoy 3 rises and it can never be turned in the oppositedirection.

If so is required, the transmission unit 2 can be designed, so thatmotive force, with which the anchor drum 9 acts on the driveshaft 11,can be disengaged also in the first rotational direction. This can beachieved by a controllable return blocking mechanism 51 of the anchordrum, or preferably with the use of a sliding clutch 55 for the anchordrum, as will be described below. The drive of the driveshaft 11 canthen be disengaged, when the accumulation of energy reaches its maximumaccumulation level, i.e. when the counter-weight 19 cannot be hoisted upany higher without the risk of damaging the anchor drum 15 and/or thebuoy 9. This disengagement of the drive of the driveshaft is then ended,when the buoy 3 starts sinking, so that the anchor drum 9 drives thedriveshaft 11 anew when the wave starts rising again. The energyabsorption of the wave energy converter is hereby limited and overloadof the transmission and the generator 21 can be prevented, when theaverage wave height exceeds the level, at which the wave energyconverter reaches its maximum capacity, i.e. rated power. Even thoughthe energy absorption is hereby temporarily disengaged, the generatorcan be driven to produce maximum power output, as long as the potentialenergy stored in the counterweight can be used. The load on thegenerator 21 and the transmission 23 can hereby be limited at the sametime as maximum power output can be maintained, as soon as the averageenergy level in the waves is high enough.

An alternative method for disengagement of the driveshaft 11 from theanchor drum 9, to limit the energy absorption, is that both engagementand disengagement is done when the torque, which is transferred betweenthe anchor drum and the driveshaft, is zero. In this case a clawcoupling 55″ can be used instead of a sliding clutch, see FIGS. 5 e and5 f. When the counterweight 19 has exceeded an upper limit, the clawcoupling is disengaged as soon as the torque has been reduced to zero,see FIG. 5 f. The claw coupling is engaged again, see FIG. 5 e, when thecounterweight has reached a certain lower limit, and when the torque iszero again, which may be several wave periods later. The upper limit, asabove, must provide enough safety margins so that the counterweight 19doesn't reach the counterweight drum 15 even if an extreme wave comes.Advantages with this method includes that the disengagement mechanismcan manage a higher torque being transferred, low energy consumptiononly during transition, and minimum of mechanical wear from thedisengagement. The disadvantage is that a longer counterweight line 17is required, which can be limiting in some cases.

The anchor drum's 9 sliding clutch 55 can be mounted between the anchordrum's return blocking mechanism 51 and the anchor drum, asschematically shown in FIG. 5 a. The by the sliding clutch transferredtorque between the anchor drum and the drive shaft 11 can preferably becontrollable in accordance with some suitable electrical signal, bywhich the maximum energy absorption level in the system can be adjusted.

In an alternative design the mechanical return blocking mechanism of theanchor drum 51, does not exist, see FIG. 5 b. The driveshaft 11 is alsoin this case passing through the anchor drum 9 undivided. Instead theanchor drum's sliding clutch 55 is used as a return blocking mechanism.The sliding clutch is mounted around the drive shaft 11 with one of itscoupling sides and mounted to the anchor drum 9 with its other couplingside. The torque transfer in the sliding clutch 55 is controlled to alsogive the function of a return blocking mechanism.

In yet another alternative design there is a detached sliding clutch 55′without mechanical return blocking mechanism, see FIG. 5 c. Thedriveshaft 11 is in this case divided and the anchor drum 9 is firmlyattached to the first part of the driveshaft 11′. There is a slidingclutch 55′ between the first part 11′ and its second part 11″ of thedriveshaft, to the side of the anchor drum. The first part of the shaft11′ is journalled in bearing to an inner stay 13′ between the anchordrum and the sliding clutch at bearing 54′. The sliding clutch 55′ is,as above, used as a return blocking mechanism and its torque transfer iscontrolled in the same way as when the sliding clutch is enclosed in theanchor drum 9.

When the sliding clutch 55, 55′ is used as a return blocking mechanism,it can be controlled as visualized in FIG. 5 d. It then alternatesbetween transferring full torque and no torque at all. The anchor drum 9rotates forward, meanwhile the wave is rising, and is then fed backwardsby the below described return feeding mechanism, when the wave issinking. The alternation in torque transfer hence occurs when therotational direction of the anchor drum is turned.

The rotation of the anchor drum 9 and the rotation of the counterweightdrum 15 can also be coupled via a mechanical coupling, the abovementioned return feeding mechanism, beside with the help of theelectromagnetic coupling through the generator 21. This can be achievedwith help of, among other things, a second sliding clutch 25, herecalled the return feeding sliding clutch, see FIG. 6, which is used forcontrolling the level of torque, which shall be transferred from thecounterweight drum to the anchor drum. The level of this torque can alsobe adjustable or dirigible. This torque can be used to reverse theanchor drum 9 and by that secure that the anchor line 7 to the bottomfoundation 5 is kept in a tensed state, meanwhile the buoy 3 sinks. Thistorque can also be used for counteracting the driftage of the buoy, awayfrom the sea floor foundation, due to currents and wind at the watersurface 6.

The return feeding sliding clutch 25 can as shown be mounted in one ofthe stays 13, in which the driveshaft 11 is journalled in bearings.Gearwheel 27, 29 runs against the edges 31, 33 on the wind up drums 9and 15 respectively and these edges can then in the corresponding way betoothed. The gearwheels 27 and 29 is connected to the input- andoutput-shafts of the sliding clutch 25 and their size in relation to thegearwheels 31, 33 at each wind up drum respectively, is adapted toprovide high enough gear ratio for the rotation speed of the anchor drum9 to be high enough to wind up the anchor line 7 fast enough to keep ittense, when the floating body 3 sinks as fastest. In the shown designthe gearwheels 27, 29 is coaxially journalled in bearings and directlyconnected to the two clutch disks 57 in the return feeding slidingclutch 25, which are pressed against each other with a controllableforce, so that when so is required, a torque of desirable magnitude canbe transferred between the counterweight drum 15 and the anchor drum 9.One alternative return feeding mechanism for the anchor drum is to usean electrical motor in a corresponding way as shown in FIG. 15 i.

The gear 23, that connects the driveshaft 11 to the generator 21, cangive a stepped up rotational speed of the driveshaft so that a higherrotational speed in the generator is obtained, which enables the use ofa high speed generator. Since the power output from the generator isproportional to the mass of its rotor 21′ and its stator 21″ and to therotational speed of the generator, this is of very high importance.Further on, the gear 23 can in general be or comprise a variable gear,where it can comprise e.g. a gear with fixed gear ratio such as aplanetary gear 35, arranged as input stage, see FIG. 12 e. The outgoingshaft of the planetary gear is then connected to the input shaft of avariable gear 37 (CVT), of which output shaft is connected to the firstof the generator's part, like its rotor 21′. The generator stator 21″,and the casing of these gears is fixed to each other and thecounterweight drum 15 and can rotate freely as one unit around thedriveshaft 11. The gear ratio between the driveshaft 11 and the firstpart of the generator 21′ is in this case given by the product of thegear ratio of the planetary gear 35 and the gear ratio of the variablegear 37.

The maximum rotational speed, that the generator 21 can handle, dependson the choice of generator. A suitable range for the generator's nominalrotational speed is around 1500 to 3000 rpm depending on its maximumcapacity, for which the wave energy converter 1 is dimensioned. To gearup the generator to such a rotational speed a gear ratio in themagnitude of 100 to 200 times is required, where the gear ratio alsodepends on the radius of the anchor drum and the medium motion speed ofthe buoy where full power shall be reached. When the rotational speed isstepped up, the torque is at the same time stepped down with the samegear ratio, which brings a very high input torques in the gear 23. Ahigh gear ratio can cause high transmission losses. A planetary gear 35as above provides a high fixed gear ratio, can manage very high inputtorques and has a good efficiency. The variable gear stage in the gear37 can be used to adapt the generator's revolution speed to the actualmedium wave height. Such a variable gear can e.g. be a step lessvariable gearbox or a hydraulic gearbox.

Alternatively, the transmission unit 2 can be designed with othermechanisms for accumulation of energy from the rise of the water surface6, e.g. as elastically stored energy. Any counterweight is then notrequired, and can instead be replaced by a spring, typically a coilspring 69, see FIG. 3 b. The inner end of such a coil spring is thenmounted to the stay 13, while its outer end is mounted to the casing ofthe gear 23 and is thereby coupled with the generator 21, to its secondpart. Energy can also be accumulated as gas pressure which will bedescribed below.

In the so far described designs, one single anchor drum 9 and twocounterweight drums 15 located on either side of the anchor drum canexist, as shown in the corresponding figures. One gear unit 23 and onegenerator 21 is included in each counterweight drum. One counterweightdrum 15 is hence connected to either end of the driveshaft 11, i.e. thedriveshaft is mounted between the two counterweight drums and thedriveshaft is journalled in bearings in the stay or the frame 13.

The movements of the two counterweight drums 15 can be synchronized withthe use of a link shaft 58, that is journalled in bearings in the stay13 parts and has gearwheels 29 at both its ends, which concurs with thetoothed edges of the counterweight flanges 33, see FIG. 2 f. Thegenerator arrangements 21 are freestanding but the counterweight 19 mustbe kept on the same horizontal level so that the distance between thecounterweight and the anchor drum is the same in both arrangements.Otherwise the centre of gravity in the wave energy converter 1 can bedisplaced, so that the power unit can turn in a faulty manner againstthe waves, with deteriorated capture ratio between the waves and thebuoy 3 as a consequence. The link shaft 58 is in the showed design alsoused for achieving the return feeding mechanism from the counterweightdrums 15 to the anchor drum 9. For this it also has a gearwheel 27,which concurs with a ring gear on one of the anchor drums flanges 33 ina similar way as for the return feeding mechanism shown in FIG. 6.

The motion of the two counterweight drums 15 can be synchronized thanksto a link shaft 58 which is journalled in bearings in the stay 13 partsand has gearwheels 29 at both ends, which concur with gear rings on thecounterweight drums' flanges 33, see FIG. 2 f. The generatorarrangements 21 are freestanding but the counterweights 19 must be kepton the same horizontal level, so that the distance between thecounterweight and anchor drum is the same in both arrangements. In othercase the wave energy converter's 1 centre of gravity may be displaced,so that the wave energy converter can turn incorrectly towards the waveswith decreased power transfer between the wave and the buoy as aconsequence. The link shaft 58 is in the presented design also used forachieving the return feeding from the counterweight drums 15 to theanchor drum 9. For this purpose it also has a gearwheel 27, which concurwith a gear ring on one of the anchor drum's flanges 33 in a similar wayas for the in FIG. 6 presented return feeding mechanism.

Since the link shaft 58 is made in one piece, to be able to rigidlyconnect the rotational motion of the counterweight drums 15, anothertype of sliding clutch for the return feeding mechanism must be used.The sliding clutch of the return feeding mechanism 25′ is in this caselocated between the larger gearwheels 27, which concurs with the flanges31 of the anchor drums 9, and the through going link shaft 58, at whichthe gearwheels are fixedly mounted. Instead of driving with the help ofconcurring gearwheels as shown in the figures, a belt-drive orchain-drive can for example be used.

The stay 13 includes in the designs in accordance with FIGS. 2 a-2 b twofrom the buoy's 3 underside protruding stay parts, each of whichincludes a bearing 54 with a return blocking mechanism 53 for thedriveshaft 11, also compare FIGS. 5 a and 5 b. Such a design of thetransmission unit 2 with an along the driveshaft centralized anchor drum9 and on both sides of this arranged counterweight drums 15 withbelonging gear 23 and generator 21, gives a symmetrical weight load onthe buoy and also a more symmetrical load due to currents in the watercompared to the case where only one counterweight drum with belonginggenerator and counterweight 19 is used, which is connected to one end ofthe driveshaft 11.

The transmission unit 2 with the anchor drum 9, the driveshaft 11, thecounterweight drums 15, the gear mechanisms 23 and the generators 21,can as an alternative be carried in a machine body or in a driveshaftframe 141, as shown in FIG. 2 g. The machine body includes a surroundingframe shaped part 143 and a number of shaft stays 145, which runsbetween the long, opposite sides of the frame part and which correspondsto the above described stays or stay parts 13. The shafts of thetransmission unit are journalled in bearings in the shaft stays. Thenumber of shaft stays is dependent on different design alternatives. Theframe 141 is secured to the buoy.

In the case where a planetary gear 35 is used, a somewhat differentdesign is possible. A planetary gear is composed by a planet carrier161, at which a number of planet gears 163 are journalled in bearings inan orbit on the inside of a ring gear 165 and around a sun gear 167, atwhich the planet gears are in gear wheel engagement, see FIG. 12 a. Whenthe planet carrier rotates and the outer wheel, the ring gear, is fixed,the planet holder drives the inner wheel, the sun gear, to rotate, whichsteps up the rotation speed? Alternatively the sun gear 167 can bedriven by the rotation of the ring gear 165 while the planet holder 161is held in a fixed position, which also steps up the rotation speed. Asabove, this can be utilized, so that the planetary gear 35 and thegenerator 21 e.g. is located inside the counterweight drum 15 and atfirst hand so that both the planetary gear's ring gear 165 and thegenerator 21″ are fixed to the counterweight drum, compare e.g. FIG. 2b.

Alternatively only the planetary gear 35 can be located inside thecounterweight drum 15 with the ring gear 165 fixed with thecounterweight drum. The generator stator 21″ is then instead fixed tothe buoy 3 as with the frame 141, see FIG. 2 g and also FIG. 3 d. Thedrive shaft 11 is journalled in bearings and can rotate freely both atthe entrance and exit of the counterweight drum. The shaft load, whichis given by the counterweight 19, is taken up by the driveshaft, whichis carried by the shaft stay 145 in the driveshaft frame 141. Theplanetary gear 35 thereby gets a low shaft load. The system functionremains the same but such a design can simplify the electricalconnection and encapsulation of the generator 21 and also simplify theaccess at service and maintenance. The levy in mass can also be reduced,i.e. the total angular momentum, since the stator 21″ in this casedoesn't need to be rotated, which can be of some significance. Alsoother types of gearboxes can be used in a similar way, at which e.g. thecasing or the cover of the gearbox is fixed with the counterweight drum15. A planetary gear's ring gear in this case corresponds to thegearbox's house or casing.

The gear ratio in a planetary gear is given by the difference betweenthe number of teeth on the planet gear and the sun gear. In FIG. 12 a aplanetary gear is shown with one gear steps but it is possible to buildin additional gear steps. This can then be according to the principlethat two or more planetary gears are coupled with the ring gears fixedto each other. Up to three steps are commonly used which givesrelatively low transmission losses. Every step is usually chosen with agear ratio between 5 and 10, which gives a gear ratio up to 300 withthree steps. The higher power the wave energy converter 1 is dimensionedfor, the larger diameter the anchor drum 9 needs to have, since theanchor line 7 requires a larger diameter at larger dimensions. Anincreased diameter of the anchor drum leads to lower rotation speed inrelation to the vertical motion of the wave, which leads to that a waveenergy converter with larger capacity require a higher gear ratio toachieve the correspondent rotation speed in the generator 21.

In FIGS. 11 d and 11 e is in the same way as in FIGS. 11 b and 11 cschematically presented how the drive of the generator 21 can beachieved for a generator with a with the buoy 3 fixed stator.

The buoy 3 will at the wave motions apart from moving vertically alsoalways change its angular orientation around a horizontal position,which is taken at a completely calm sea. The driveshaft 11 then rockssideways all the time, which can get the anchor line 7 and thecounterweight line/lines 17 to slide and rub against each other on theanchor drum 9 and the counterweight drum/drums 15. A track guidingmechanism can then be used, which see to it that resp. lines are windedup in a regularly way. One possibility is to use helicoidal grooves 39,41, 43, 45 on the drums' 9, 15 cylindrical winding up surfaces, see FIG.3 c. When two counterweight drums are utilized, the direction of theirhelicoidal grooves can be opposite, i.e. one of the helicoidal grooves39, 41 is right handed while the other helicoidal grooves 43, 45 is lefthanded, to maintain a symmetrical load on the wave energy converter 1,due to the motive force relating to the counterweights 19 and the anchorline 7, to some extent. Helicoidal grooves according to 39, 41, 43 and45 with a shape that follows the profile of the lines can alsosignificantly increase the length of life of the lines since the contactsurface between line resp. the wind up drum is increased.

If only one anchor line 7 is used, the point where this line affects theanchor drum 9 is moved along the axis, when the line is more or less iswinded up and unwound. To achieve a more symmetrical load in the casewith two counterweight drums 15 the anchor line 7′ can be in a loop, sothat it runs from one side of the anchor drum at helicoidal groove 41,down to the sea-floor foundation 5 and via a pulley 40, which isjournalled in bearing to the sea-floor foundation 5, and back up againto the other side of the anchor drum via helicoidal groove 43. Theanchor line is then in both its ends more or less winded up on theanchor drum wind up surface in two segments with helicoidal grooves 41and 43, which have helicoidal grooves in opposite directions. It is alsopossible to divide the anchor line by a Y-coupling located a distanceunder the wave energy converter, see FIG. 15 a and the descriptionbelow.

As will be described below, two anchor drums 9 v, 9 h can be placed oneither side of a centrally located counterweight drum 15. Helicoidalgrooves for resp. line 7, 17 can then be arranged in a way correspondingto what is shown in FIG. 3 c. The counterweight drum can then have twosegments with helicoidal grooves with opposite directions, this is notshown.

As an alternative or a complement to the helicoidal grooves on thewinding up drums 9, 15 guide rollers 171 can be used to guide bothcounterweight lines 17 and the anchor line 7 around resp. wind up drum,see FIGS. 13 a, 13 b and 13 c. The guide rollers are driven by threadedrods 173, which are rotated in pace with the drums. The threaded rodsfor resp. counterweight drum 15 has screw-threads in the oppositedirection as seen in FIG. 13 a, so that the counterweight lines 17 isguided in opposite direction to each other, which is important for thecentre of gravity of the wave energy converter to remain centralized.

Two threaded rods 171 are used for each winding up drum 9, 15 and thesetwo are rotated by a common teeth belt or chain 175, which turns belt-or chain-wheels 177. The guide ends of the guide rollers 171 areconnected to end pieces 179, through which the threaded rods passes andwhich guides the guide rollers along the threaded rods. The guidedrollers are journalled in bearings at the end pieces and can rotatealong with resp. line 7, 17 to minimize friction and wear. The ends ofthe threaded rods 173 are journalled in bearings at the driveshaft stay141.

Yet another alternative to achieve safe wind up is to use trawl drums,not shown, as is known from the fishing industry.

To minimize the risk that the counterweights 19, in the case where twocounterweights are used, and their lines 17 tangled with each other thecounterweights can be mechanically connected together by a suitablestiff mechanical structure, which holds them physically separated fromeach other. E.g. a counterweight frame 151 can be used, see FIGS. 3 eand 3 f. The counterweight frame can be shaped so that it does not rubagainst the anchor line 7 and also prevent entanglement with it, e.g.with a rectangular, quadratic or rhombic shape according to FIG. 3 f orwith the shape of a closed curve, such as a round curve, not shown.

The buoy 3 can generally have the shape of a plate, which can be oblong.Such an oblong plate can then in a convenient way be positioned, so thatit mostly has its longer end towards the wave direction. The width ofthe buoy 3 can be adapted to the average wave length of the waves at thesea surface, so that the buoy has a larger width at larger medium wavelength. Different methods can be used to stabilize the buoys' positionin relation to the wave direction. The rotating motion of the waterparticles through the waves in combination with the traction forcetowards the centre above the foundation 5 can be utilized by introducingfins, see FIGS. 2 d and 2 e, on the buoy's 3 underside. Further thebuoy's shape can be adapted. The driveshaft 11 can instead of beingcentralized under the buoy as shown in FIGS. 2 a and 2 b, in parallelwith the plates length going direction, be a bit displaced in thedirection towards the waves.

For the mounting of the transmission unit 2 inside the buoy 3, as shownin FIGS. 2 c, 2 d and 2 e, the buoy must have such a size, that it canhold the transmission unit. Seen from the side, in parallel with thedriveshaft 11 the buoy can in this case have the shape in the form of anellipse, i.e. generally an elliptic cylinder. It can have a relativelylarge section area against the water surface 6 at the same time as itcan be pulled against the wave direction with less water resistancecompared to a completely rectangular section area. The buoy 3 can haveone or more fins 4 in its back part, seen from the wave direction, whichcan contribute to steering the buoy straight against the wave direction.

The transmission unit 2 in this design can be mounted in thetransmission unit space 20, whereby the transmission unit in whole orpartly can be made dry and thereby be protected against growth andcorrosion and a simpler and cheaper sealing solutions can also be used,see FIGS. 2 c, 2 d, 2 e and 2 f. When the transmission unit space 20 ismade dry, it also contributes with its buoyancy to the buoyancy of thebuoy 3. The transmission unit space can for this purpose at the top besealed by a cover or a service hatch 121, so that the transmission unitspace constitutes an air pocket. To create and maintain the drainage ofthe transmission unit space 20 an air pump 123 can be used. The air pumpcan be driven by the link shaft 58, e.g. through a belt 125, and pumpair into the transmission unit space which gets the water level to bepushed down, so that the transmission unit 2 is maid dry and the desiredair pocket is achieved. The air pump can be mounted at one of the shaftframes 145, at which the driveshaft 11 is journalled in bearings. Theair pump 123 can alternatively be driven by an electrical motor, notshown.

When the wave energy converter is taken into operation, the servicehatch 121 over the transmission unit 2 is closed and the water level inthe transmission unit space 20 is pushed down by the air pressure, whichthe air pump 123 produces. The water level outside varies during thewave period correspondingly to the motive force between the sea floorfoundation 5 and the wave and also the mass-moment of inertia incounterweight 19 and buoy 3. At service first of all the anchor drum 9is disconnected, then the pressure in the transmission unit space isleveled to the air-pressure outside, so that the water level rises, andthereafter the service hatch 121 can be opened and service be performed.With the right dimensioning and when the motive force from thefoundation 5 is disconnected the water level can be leveled just belowthe driveshaft 11, so that sealings and air pump 123 never gets underthe water surface 6.

At major service the complete driveshaft frame 141 with includingcomponents as shown in FIGS. 15 g, 15 h and 15 i, can be lifted out andreplaced with a replacement unit. The counterweight 19 can be hitchedunder the buoy 3 meanwhile the exchange is performed. Service of thewave energy converter's transmission, generator and electronics can thenbe performed ashore.

In the design with the transmission unit 2 and the driveshaft 11 placedcentrally in the buoy 3 the buoy's angular modulation can be used moreefficiently. The buoy does follow the water surface, which gives anangular modulation at troughs and wave crests. When the wave rises, thedriveshaft 11 rotates and the shaft stays 145 are then disengaged, sothat the buoy 3 can rotate backwards with the wave's waterline withoutaffecting the drive. When the waves turns downwards, the driveshaft islocked against the shaft stays, which causes the driveshaft to turnforward in pace with that the buoy following the angular modulation ofthe wave. This in turn gets the counterweight drum 15 to rotate inforward direction and act to accumulate energy in the counterweight 19in the same way as during the vertical motion in up going direction. Thelarger diameter the anchor drum 9 has, the lower input rotation speedthe system gets in relation to vertical motion, while rotation speedfrom the angular modulation is the same irrespective of the anchordrum's diameter. The wave energy converter 1 can in this way bedimensioned with a larger anchor drum 9 to achieve an enhanced effectfrom the angle modulation in relation to the motive force from thevertical motion but must then also have a large enough width towithstand the in the same pace increased torque, which is transferred tothe buoy 3 from the counterweight 19, when the driveshaft 11 is lockedagainst the shaft stays 145.

The function of the wave energy converters 1 is with advantagecontrolled by a computerized control system, not shown, which especiallycontrols the counterweight span level and compensates for varyingaccelerations and retardations to achieve as equalized power level aspossible in relation to the current wave climate. The control system canalso be used for controlling the torque transfer in the anchor drum'ssliding clutch 55, 55′ and the return feeding's sliding clutch 25, 25′,control of locking mechanisms, not shown, control hitching ofcounterweight 19 and sea-floor foundation 5 in the driveshaft frame 141at transport and service, and also logging of system function and wavedata. The control system is supplied with energy from a battery, notshown, which is continuously charged by the generator 21.

The control system controls the counterweight span level and monitorsthe wave energy converters 1 functionality with the help of sensors, notshown, especially for rotation angles/speeds of the rotatable parts, thegenerator's 21 electrical power output and the buoy's 3 movements.

The control system can control the counterweight span level by analysingdata from a sensor, not shown, that is mounted in the counterweight drum15 and which continuously tells the system, at which angle it has inrelation to the gravitational direction or the shaft stay 13. Thecontrol system can thanks to this track the counterweight 19 positionand turning points by calculating the number of revolutions of thecounterweight and exactly where it turns. The turning points for eachindividual wave period are logged. An algorithm calculates if thecounterweight span has a tendency to drift upwards or downwards byanalysing the turning points during a time period. If the counterweightspan is drifting upwards, the counterweight 19 can be lowered in aquicker pace, which leads to that a higher power output is generatedfrom the generator 21 and vice versa. The length on the time period isdecided from the accumulation capacity, i.e. the length of thecounterweight line 17. The higher capacity, the longer time period canbe used in the calculation, which in turns gives smaller adjustments ofthe generator's power output.

Two sensors, not shown, measure the electrical power output and therotation speed of the generator 21. These values are recalculated by thecontrol system to show the torque level over the generator. The controlsystem use the torque value to compensate for the counterweight's 19g-force, which varies due to the mass-moment of inertia and affection bythe acceleration force and water resistance, which arises due to thebuoy's 3 motions in combination with variations of the driveshaft's 11rotation speed. At a trough, the counterweight 19 is accelerated in adirection away from the gravitational direction, which gives anincreased g-force, and at a crest the counterweight is acceleration adirection back to the gravitational direction, which gives a lowerg-force. By regulating the counterweight's velocity of fall inaccordance with the varying torque, which loads the generator 21, thepower level can be stabilized.

As given from the discussion, for the counterweight's 19 turning pointsnot to drift to the end positions of the counterweight, thecounterweight's velocity of fall, i.e. the medium rotation speed of thecounterweight drum 15, must be balanced against the driveshaft's 11rotation speed. When the medium turning point is moved downwards, thecounterweight's velocity of fall must be reduced, which leads to areduced power output from the generator 21 and vice versa. By regulatingthe counterweight's velocity of fall and thereby the counterweight spanlevel the power output from the generator can be kept as even aspossible in relation to mean energy level in the current wave climate.

Regulation of the counterweight span level can be achieved in differentways. Regulation of the electrical load on the generator is likely thesimplest and most cost efficient but there are also other possibilitiesas described below.

The mechanical resistance in the generator 21 depends on the electricalload, which is laid over the generator's poles. When the electrical loadis increased, the electromagnetic coupling over the air gap 21″ in thegenerator is increased and thereby the mechanical resistance in thegenerator, which gets the counterweight 19 to fall slower, since thestate of equilibrium between the generator and the counterweight ismoved to a lower rotation speed and vice versa, se the regulation rule,which is shown in the diagram in FIG. 16 a. Since the generator's poweris a product of the rotation speed and the torque, the power levelbecomes even, meanwhile the rotation speed varies in the oppositedirection to the g-force and the input torque. This works due to thatthe top rotation speed in a generator in general is higher than thenominal rotation speed. The generator should manage a top rotation speedthat is at least 50% higher than the nominal.

At a constant electrical load a state of equilibrium becomes present,i.e. the rotation speed of the generator 21 becomes present, which givesan equally high mechanical resistance in the generator as the motiveforce given by the counterweight 19, as earlier described. By regulatingthe generator's ingoing mechanical torque the state of equilibrium isdisplaced and thereby the rotation speed, at which the state ofequilibrium becomes present. The input torque can be adjusted with agear box with a so called variable gear ratio 37, CVT (“ContinuousVariable Transmission”), which can constitute or be included in the gear23. A lower gear ratio gives a higher torque and a lower rotation speed,which in turn balance each other out, but a higher torque also makes thestate of equilibrium, between the generator 21 and the counterweight 19,to take place at a higher rotation speed, which increases thecounterweight's velocity of fall, and vice versa, compare with theregulation rule, which is shown in diagram 16 b. One type of CVT is CVET(“Continuous Variable Electronic Transmission”) with input-output shaftsaligned, as schematically shown in FIGS. 12 c, 12 d. These figures areonly symbolic, since the manufacturer does not want to reveal detailsregarding its mechanical design. Variable transmission gear boxesusually only manage limited torques and a relatively low maximum gearratio. To minimize the ingoing torque and increase the gear ratio aplanetary gear 35 can be coupled in before the variable transmission, asshown in FIG. 12 c.

The return feeding's sliding clutch 25, 25′ between the counterweightdrum 15 and the anchor drum 9, which according to above can be used forkeeping the anchor line 7 tensed, can at the same time be used forreducing the torque given by the counterweight 19, which displaces thegenerator's 21 and the counterweight's 19 state of equilibrium in thesame way as a variable gear does, see the regulation rule shown indiagram in FIG. 16 c and also compare with the diagram in FIG. 16 b.Full power of the generator and full speed of the counterweight isreached, when the return feeding mechanism's sliding clutch 25, 25′ iscompletely disengaged, so that the full torque from the counterweightloads the generator. When the medium wave height sinks, the torque inthe return feeding's sliding clutch increases, which lowers the torqueover the generator 21 and hereby the counterweight's velocity of fall isreduced. As sliding clutch e.g. a magnetic particle clutch can be used,which gives low heat losses at low rotation speeds. The torque can beregulated very precisely with the help of the level of a feedingcurrent, so that the higher the current the higher the transferredtorque becomes and thereby also the higher break action.

By using a cone shaped counterweight drum, not shown, the radius for thecounterweight line 17 point of contact around the counterweight drum canbe increased the higher the counterweight 19 is winded up. The radiusand thereby the torque increases the higher the counterweight is hoistedup and thereby makes the generator 21 to rotate faster. In this way, thecounterweight's 19 velocity of fall and the generator's power outputincreases with an increased medium wave height. This principle forregulation of the counterweight's span is self-regulating and hence doesnot need to be regulated by a control system as the other methods, butlacks the ability to compensate for variations in the counterweight'sg-force or the force with which the counterweight affects the drivepackage, i.e. mainly the motive force in the counterweight line.

It is possible to design a wave energy converter 1 for automaticinstallation. The starting position is then, that the sea-floorfoundation 5 and the counterweight 19 is hitched at the stay's 13 partsor at the frame 141 with corresponding lines 7, 17 completely winded up.The wave energy converter is connected to the electrical distributionnetwork and the control system is started. The disengagement mechanismfor the return blocking mechanism of the anchor drum is put in lockedposition according to a control signal from the control system, so thatthe anchor drum 7, cannot be disconnected, despite that thecounterweight/-s are in their top positions. In the shown designs thismeans that the sliding clutch 55 mounted around the return blockingmechanism of the anchor drum 51 is put on maximum force- or torquetransfer, which is enough to carry the entire weight of the sea-floorfoundation. The sliding clutch 25 of the return feeding mechanism can bedisengaged.

Then the control system loosens the hitches, not shown, that holds thecounterweight 19 and the sea-floor foundation 5, whereby the sea-floorfoundation starts to fall towards the bottom 8 of the sea-floor. Theanchor drum's line 7 is then unwound and the driveshaft 11 starts torotate and drive the generator/generators 21. The control systemregulates for maximum power and thereby the sea-floor foundation's 5velocity of fall is slowed down as much as possible, by the electricalpower that is produced. Further on the buoy 3 is preferably equippedwith an echo-sounder, not shown, that measures the water depth on thesite, where the installation takes place. The anchor drum 9 is equippedwith the same type of sensor, not shown, as is mounted on thecounterweight drum/-drums 15 and the control system can in this waymeasure how much of the corresponding anchor line 7 that is unwound fromthe anchor drum. The control system can with help of these valuescalculate when the sea-floor foundation 5 starts to approach the bottom8. To reduce the force of impact the sea-floor foundation's velocity offall is slowed down by means of the return feeding sliding clutch 25.When the sea-floor foundation 5 reaches the bottom 8, the driveshaft 11stops to rotate and the counterweight/-counterweights 19 instead startsto fall and continues to drive the generator/-generators 21. Thedisengagement mechanism for the anchor drum's 9 rotation in relation tothe driveshaft is activated, so that the anchor drum can rotate in onedirection in relation to the driveshaft. In the shown design this means,that the sliding clutch 55 in the anchor drum is put in normal mode,which means that the by the sliding clutch transferred force is reducedso that the force is not enough to lift the sea-floor foundation 5. Thecontrol system is thereby put into operation mode.

The outer electrical connection of the generator 21 can be achievedwithout the use of slip rings, brushes and similar, even when thegenerator stator″ 21 is mounted inside counterweight drum 15. Thegenerator stator 21″ includes, in a conventional way, electricalwindings, in which electrical power is induced at rotation and which areconnected to an electrical cable 41, which is partly winded up on thecounterweight drum in parallel with the counterweight line 17, see FIG.4, but closer to the anchor drum 9. The electrical cable extends fromthe counterweight drum 15 down to a movable connector 43, which can movealong the anchor line 7. At the connector the electrical cable 41 isconnected to yet another electrical cable 45, which e.g. extends to aspecial connector buoy 45. Hereby the wave energy converter 1 can manageto rotate, when the waves change direction, without lines and cablesgetting entangled with each other.

Since the first electrical cable 41 is winded up on the same drum as thecounterweight 19, the connector 43 to will slide along the anchor line15 with mainly always the same distance below the counterweight. Herebyit can be avoided that the counterweight and the electrical cables 41,45 comes to close to each other.

At an alternative way for energy accumulation the energy can be absorbedas a gas pressure in one or more tanks. Such a wave energy converter 1is schematically shown in FIG. 9 a. Here the anchor drum 9 only needs tobe connected to the driveshaft 11 via a return blocking mechanism 53,compare the return blocking mechanism in the shaft stay 13 in FIGS. 5 aand 5 b. Any stays are not required, the driveshaft can instead bejournalled in bearings directly in the generator housing or thegenerator casing 71, which replaces the counterweight drum 15 and whichin this case can enclose a fixed gear mechanism such as a planetary gear35, generator 21 and a compressor/gas pump 73. The casing is fixed tothe buoy 3, such as to its underside as shown in the figure or alsocentralized in the buoy, if a transmission unit space 20 according toabove is used for mounting of the transmission unit 2. From thecompressor/gas pump 73 a gas pipe 75 runs to the gas tanks 77,preferably located at or in the buoy. The gas tanks are also coupled toan over pressure valve 79 and a pneumatic motor 81. At this motor'soutgoing shaft 85, gearwheel 87 is located, which acts together withteeth on the anchor drum's 9 flange 31.

The compressor/gas pump 73 can be a so called scroll pump and it thenhas a movable part 89, which is fixedly connected with the generator 21stator 21″, and one to the housing 71 fixed part 91. The driveshaft'sreturn blocking mechanism 53 here acts against the housing.

When the driveshaft 11 is turned by the rising buoy 3 in this design, agas pressure is built up, by the scroll pump 73, in the gas tanks 77.This gas pressure corresponds to accumulated energy. In pace with theincreasing gas pressure, the counteracting force against the driveshaftrotation also increases. Higher waves, that give rise to a quickermedium rotation speed of the driveshaft 11, thus build up a higher gaspressure and which thereby gives a higher counteracting torque betweenthe generator rotor 21′ and stator″. The control system hence does notneed to actively control and optimize the operation since theequalization occurs through inertia in the pneumatic pressure. Since theenergy accumulation take place by a pneumatic pressure being built up,the overpressure valve 79 can possibly be used instead of the slidingclutch 53 between the anchor drum 9 and the driveshaft 11. The slidingclutch though has an advantage by that it protects against thruststrains. When the anchor drum 9 does not turn by its coupling to theanchor line 7, as when the buoy 3 is sinking, it instead turns backwardsto stretch the anchor line by that the pneumatic motor 81 rotates anddrives the gearwheel 87, which acts on the flange 31 of the anchor drum.

Even with the use of gas return pressure it is possible to let thegenerator stator 21″ be fixed to the buoy 3 and instead connect thecompressor 73 to the planetary gears 35 ring gear 165, see FIG. 9 b. Inthis case is the generator's stator is fixed to the generator housing71. The generator chassis 91 is also fixed to the generator housing,meanwhile the compressor's 73 gear 95 on its driveshaft 93 is connectedto the planetary gear's ring gear, either directly as is shown or via ateeth belt/chain. The ring gear rotates freely around the ingoingdriveshaft 11.

This design of the transmission unit 2 can have the followingadvantages:

-   No sling clutches are required in the anchor drum 9 or in the return    feeding mechanism.-   No counterweights are required and thereby there is no g-force and    no counterweight span that must be regulated, since the higher wave,    the higher gas pressure and torque over the generator 21.-   Possible problems with counterweights and lines, outer electrical    cables, effect of accelerations, centre of gravity etc. can come    down completely or be reduced.-   The case that no counterweight is used gives lower movable weight    and thereby the sea-floor foundation 5 can also be made smaller,    i.e. with smaller mass. The buoy's 3 lifting force can also be    reduced with as much.-   Manage shallower installation depth-   Only the anchor drum needs to be exposed to the ocean water    meanwhile other components can be encapsulated.-   The housing for the gear mechanism and the generator can be made    with smaller diameter than the one in the earlier described design    used counterweight drum.

The same type of transmission unit 2 as have been described above can beused in other designs of the wave energy converter as becomes evidentfrom FIGS. 7 a, 7 b and 7 c. Instead of the sea-floor foundation thereare here sea-floor fastening devices 61, 63 fastened to the sea-floor.8. These sea-floor fastening devices are shaped like frames or pillars,which reach upwards from the sea-floor, and the driveshaft 11 in thetransmission unit is journalled in bearings in the frames or at thepillars. In FIGS. 7 a and 7 b two vertical pillars are used, which arelocated completely beneath the water surface 6 and stretches up from thesea-floor, and the driveshaft 11 in the transmission unit is journalledin bearings to these pillars. In the designs according to FIGS. 7 a and7 b the anchor line 7 is fixed to the buoy. In FIG. 7 b the transmissionunit is mounted so close to the bottom of the pool of water that thecounterweights are instead shaped like floating bodies 19′. The frameaccording to FIG. 7 c includes two vertical pillars, which reachesupwards from the bottom 8 over the water surface 6 at the side of thebuoy 3. The pillars are at the top connected by a horizontal beam 64,which is located above the buoy and from which stay parts similar to thestay 13 above protrudes downwards. The driveshaft 11 in the transmissionunit is journalled in bearings in these stay parts. It can be especiallyobserved, that at the design according to FIG. 7 c, energy is absorbedfrom the waves only when the water surface 6 and the buoy 3 sinks incontrary to the other designs, where energy is only absorbed from thewaves, when the water surface and the buoy rises. Hereby the buoy mustbe given a weight that is greater than the counterweight's 19 and begiven enough volume/buoyancy, so that it shall still be able to stayafloat at the water surface 6. This is shown in FIG. 7 c by that thebuoy 3 is fixed with a ballast 5″. In this design the counterweight 19line 17 is winded up around the counterweight drum 15, when the wavesinks, which significantly reduces the motion span and variation ing-force. With the right dimensioning and with periodical waves thecounterweight can in principle be held still. It is also possible tokeep the counterweight above the water surface 6, which gives a highermotive force in relation to the counterweight's mass. This design isespecially suited for places, where there are already foundations, e.g.at wind power plants, where the counterweight and its line 17 can runinside the mast, or at oil platforms.

An alternative design of a wave energy converter 1 with a transmissionunit 215 according to FIG. 15 a with a centrally, between two anchordrums 9 v, 9 h located counterweight drum 15 is shown in FIG. 7 d. Inthis variant the driveshaft 11 is driven by a weight or load 211, whichhangs beneath the buoy 3 in an elastic organ 213, which for example caninclude springs or air springs. At the weight the anchor lines are alsofixed. The weight 211 can have a considerable mass compared to the buoy3 or generally in relation to other parts of the wave energy converter.The forward drive of the driveshaft occurs through joint action betweenthe buoy 3 and the weight 211. When the buoy after having passed a wavecrest sinks, the buoy also moves downwards. Then when the buoy slowsdown and turn in the next trough, the weight 211 continues due to itsinertia to first move downwards, which stretches and prolongs theelastic organ 213 and unwinds the anchor lines 17 so that the anchordrums 9 v and 9 h is rotated and in turn drives the driveshaft torotate. When the elastic organs are prolonged, their traction force onthe weight 211 increases, so that its ongoing motion downwards isgradually stopped. Thereafter the force from the elastic organs becomesso great, that the weight will move upwards. This consequently occurs atthe buoy's 3 rising movement. When the buoy 3 then slows down again toturn in the next crest, the weight continues to move upwards due to itsmass-moment of inertia. The elastic organs 213 are then pulled togetherand thereby their traction force on the weight 211 is reduces, so thatit is no longer balanced by the gravity force, which affects the weight.At the same time the anchor drums 9 can be returned and tense the anchorlines 7 for the next drive of the driveshaft 11. The weight is thengradually slowed down to a stop and after that again starts to movedownwards.

The counterweight 7 runs through a through going hole in the weight 211down to the counterweight 19, which moves with a phase shift to the wavemotion, which can reduce its vertical motion and reduce the size of itsaccelerations and retardations at the wave motion, so that the torque,which loads the generator 21, becomes a bit more even, which therebyrequires less regulation of the rotation speed. Such a design can e.g.be advantageous at large water depths, where it can be difficult to usean anchor line 7 fixed at the bottom 8 for driving of the driveshaft.

In one design, in which the wave energy converter is mounted in a windpower plant, it is possible to integrate the transmission from theturbine blades with the drive from the waves, so that the same gearboxand generator can be used, see FIGS. 8 a, 8 b and 8 c. The transmissioncan closest be compared to the one shown in FIGS. 15 a, 15 b and 15 e,which shall be described below. The transmission model with a fixedstator according to FIG. 15 f can also be used in a similar way but thisis not described further here. The main difference is the mounting ofthe planetary gear 25 in relation to the generator's stator. Thefunction in the planetary gear is in this design to combine the drivefrom the wind- and wave motions, by letting the wind power plant's rotorrotate the planet gear carrier 161, while the buoy 3 with ballast 5″drives the ring gear 165 of the planetary gear, see also FIGS. 12 a and12 b. In this way, the rotation and torque, which are obtained from thewind-resp. wave motions, can be added to each other and together drivethe sun gear 167. Neither planet carrier nor ring gear is allowed torotate backwards, which for the planet carrier is achieved by the backlocking mechanism 53 in the shaft stay 13 and for the ring gear byslipper clutch 201, which has a function similar to a back lockingmechanism. The slipper clutch 201 has the equivalent function as theanchor drum's slipper clutch, see FIG. 5 b and descriptions thereof, butis in this design located between shaft stay 13 and planetary gear 35,which makes it possible to limit the torque and energy absorption forboth wind- and wave motions with one and the same slipper clutch.

The generator 21 is mounted alone in the counterweight drum 15 withconnected counterweight 19, which gives the same equalizationcapabilities as is described for the other designs. The return feedingof the anchor drums is also done in the same way from the counterweightdrum 15 via ring gear 29 and tooth band/chain 175 to the link shaft 58,which in turn is coupled in the corresponding way to the anchor drums 9v and 9 h. The diameter of the anchor drums 9 v and 9 h in combinationwith the buoy 3 and the weight of the ballast 5″, determines the torquewhich is put over the ring gear 165 of the planetary gear, and whichrotation speed the ring gear gets. These parameters are chosen to matchthe torque from the wind turbine and the generator's size. As long asthe torque, which is obtained from the drive of wind and wave, is higherthan the counteracting torque, which is given by the counterweight 19,energy can be accumulated in the counterweight 19 from both wind- andwave motions. Since the torque from the wind power plant's rotor 204varies dependently on the wind-force while the torque from the wavedrive is constant, it may be necessary to mount a variable transmissiongearbox before the planetary gear in the same way as shown in FIG. 12 e,but the variable transmission gearbox in this design adjusts the torquefrom the wind drive to the wave drive after the current wind-force. Toprevent the tower 207 of the wind power plant to be damaged by the buoy3, some kind of sledge mechanism is used, not shown, which guides thebuoy along the tower of the wind power plant. Breaking gearboxes is abig problem for today's wind power plants. The transmission of the waveenergy converter can also be used in a wind power plant without wavedrive to utilize its capabilities to limit the torque and energyabsorption. In this case the same type of transmission design asdescribed in FIG. 3 d can be used but without the anchor drum 9. Thewind power plant's rotor is directly connected to the driveshaft 11, asshown in FIGS. 8 d and 8 e. The counterweight can run inside of the windpower plant's tower 207. When used in a wind power plant, gas returnpressure can also be used instead of a counterweight as shown in FIG. 8f. This transmission design is described in more detail in connection toFIG. 9 b. The counterweight can then be left out and its mass-moment ofinertia will then not have any effect, which can be of an advantage.

In the designs described above, the electromagnetic coupling between thegenerator's 21 rotor and stator is utilized in most cases, while inother cases an in a special way designed transmission is used forachieving a continuous drive of the generator. Energy accumulation andreturn feeding can be done in different ways. In general, a wave energyconverter 1 can include components as will be seen in FIG. 10 a. Ananchor drum 9 included in a transmission unit 2 is in a suitable waymechanically coupled to both a buoy 3 and to an object 8′, which can beconsidered to have a more fixed position than the buoy and which can beconstituted by the bottom, e.g. a bottom fastening device 5′, also seeFIG. 10 b, at which at least one of these two mechanical couplings 7″,7′″ includes an oblong organ, such as a flexible organ, typically a lineor a wire, but also a stiff shaft can be used in special cases. Theanchor drum can be located in a suitable way in relation to the buoysuch as under, inside or above. It can rotate in two directions as shownby arrows 101, 102. The anchor drum 9 drives a driveshaft 11 at itsrotation in one direction, which can then only rotate in one direction,shown by the arrow 103. The driveshaft is mechanically coupled to thegenerator 21, whereby the coupling is symbolically shown at 23′. Thecoupling and/or the generator is set up in a way that a part of therotational energy is accumulated in an energy accumulation device 105 atthe rotation of the driveshaft 11. When the driveshaft is not able toturn the generator, the energy accumulation device drives the generatorinstead. The energy stored in the energy accumulation device can also beused for returning the anchor drum 9 and for this purpose the energyaccumulation device can be coupled to the return feeding mechanism 107.

In the case which utilizes the electromagnetic coupling between thegenerator's 21 two, in relation to each other rotatable parts, thedriveshaft 11 is mechanically coupled to the first part 21′ by means ofthe coupling 23′, for driving this part to rotate in the direction shownby the arrow 23, at which the electromagnetic coupling between thegenerator's parts gives a torque corresponding to the driveshaft'srotation and also gets the other part 21″ to rotate in the samedirection, se FIG. 10 b. The generator's second part 21″ is in some waycoupled, so that it at the rotational motion, because of thedriveshaft's rotation, accumulates a part of the rotational energy inthe energy accumulation device 105. When the rotation speed of thedriveshaft is low, where it no longer is capable of turning thegenerators second part, the energy accumulation device instead drivesthe generators second part to rotate in the opposite direction asbefore.

In the designs described above, two generators 21 are used. However,since the generator with belonging power electronics and gearbox, ifany, is a relatively costly part of the wave energy converter 1, designswith only one generator can be more cost efficient. Below shall possibledesigns with only one generator be described.

In a first design with two counterweights 19 and one to the buoy 3 fixedstator of the generator 21, see FIG. 14, there is also, as shown in e.g.FIG. 26, a return feeding or link shaft 58. The link shaft couples themovement of the two counterweight drums together, so that the motiveforce from the right counterweight drum 15 h is transferred to the leftcounterweight drum 15 v. The left counterweight drum includes aplanetary gear 35, which steps up the rotation speed of the generator,and also limits the torque by means of the ring gear's coupling to theleft counterweight drum and the counterweight 19. The location of thewind up drums are moreover the same as in the above described designsand therefore, the buoy 3 in a wave energy converter designed in thisway, gets about the same stability or positioning towards the wave as inthe design with two generators. The generator 21 can be mounted in aseparate generator housing 181 with the generator's stator 21″ fixed tothe buoy, as shown in the figure, or alternatively in or at the leftcounterweight drum 15 v.

As shown, the link shaft 58 can be placed in front of the driveshaft 11seen in the wave direction. This gives a better spacing when driftingaway from the sea floor foundation 5. The drifting brings the anchorlines 7, which cannot be allowed to come into contact with thedriveshaft frame 141, to stretch out in a direction in relation to thecounterweight line in a slanting angle. Alternatively, the link shaft 58can be placed above the driveshaft 11, either in a slanting position orstraight above.

Further on it is possible to design the transmission unit 2, so thatonly one counterweight 19 is used without the wave energy converterloosing stability or positioning towards the wave direction. Insteadsuch a design can, see FIG. 15 a for a front view and 15 b for a sideview, enhance the positioning in relation to the wave direction. Theanchor line 7 is divided in a Y-coupling 191 into two sub lines andthese are led to be winded up around one anchor drum 9 v, 9 h each,which are positioned on each side of the single counter weight drum 15′.Guide rollers 193, corresponding to the ones described for FIGS. 13 a,13 b and 13 c, diverts the sub lines, so that they are winded upcorrectly on the anchor drums. The counterweight 19 runs free despitethat the anchor lines joins in a Y-coupling, since the point at thecounterweight drum and anchor drum where the resp. line is winded up ison the opposite side of the driveshaft 11. The driftage from thefoundation 5 also gives an angle for the anchor line 7, 7′, which givesextra margins. For further safety margins the Y-coupling 191 can beplaced below the lowest possible position of the counterweight 19, notshown.

In FIGS. 15 c and 15 d an alternative of a straight wind up of thedivided anchor lines 7′ around the anchor drum 9 v and 9 h is shown. Arod 221 holds the lines on a distance from each other and is placed justabove the Y-coupling 191. To decrease the risk of collision between subanchor lines 7′ and the counterweight 19, the rod 221 can be placedbelow the lowest possible position of the counterweight. One advantagewith this alternative is that the part of the anchor line 7, whichconnects the rod 221 with the sea-floor foundation 5, can be more orless stiff and e.g. be designed as a ground cable or chain, while thesub anchor lines 7′ can be more flexible for wind up around the anchordrums 9 v and 9 h. Further on the rod 221 can be designed to carry theload of itself and the undivided anchor line 7, which then leads to thata lower force is required for driving the return feeding, not shown inthese figures.

In FIG. 15 e the transmission unit in a wave energy converter is shownaccording to FIGS. 15 a and 15 b seen from below and with more details.The driveshaft 11 is here fixed only one of the anchor drums, e.g. asshown with the left 15 v. The left anchor drum 9 v, the driveshaft andthe one and only anchor drum 15′ has the same function and structure asin earlier described designs, in which the generator 21 is build-in tothe counterweight drum. The second anchor drum, the right drum 9 h, isjournalled in bearings so that it can rotate freely but its motive forceis transferred to the left anchor drum 9 v by means of a link shaft 58.The link shaft can be coupled via thereon mounted chain- or gear-wheels203 to the anchor drums by means of chains or tooth bands 205, whichalso runs over the toothed flanges 31. Alternatively the gearwheels 203can be directly connected to the anchor drums' flanges, in the same wayas shown in FIG. 2 f. The return feeding of the anchor drums is done inthe corresponding way as earlier but the slipper clutch 25″ is in thiscase coupled to the counterweight drum 15′.

In FIG. 15 f an alternative to the transmission unit according to FIG.15 e is shown. According to FIG. 15 f the generator's stator 21″ isfixed to the buoy 3 in a corresponding way as shown in FIG. 2 g. Thegenerator casing 71 is placed on one side of the single, centrallyplaced counterweight drum 15′, which results in that the transmissionunit 2 must be made wider. The anchor drums 9 v, 9 h must be placed withan equal distance from the counterweight drum for the traction force bythe counterweight 19 and the foundation 5 via the counterweight lines 7′shall remain centred in the wave energy converter. This leads to thatmore stay parts or shaft stays 13, 145 are required to carry the partsof the transmission units. It is possible to use the same design of theanchor drums as described above for FIG. 15 e. However, in this case itcan be motivated to simplify the left anchor drum 9 v by using andisplaced or free lying slipper clutch 55′ and use the extra space inthe transmission casing space 20 for the transmission unit 2, so thatthe left anchor drum 9 v can be fixed to the driveshaft's first part 11′in the same way as earlier described for FIG. 5 c while the driveshaft'ssecond part 11″ on the other side of the slipper clutch comprises or isdirectly connected to the ingoing shaft to the gear 23 and thecounterweight 15′ rotates around this second part.

In FIGS. 15 g and 15 h an alternative transmission unit according toFIG. 15 f is shown, in which the mechanics is to a larger extentencapsulated. The power transmission between driveshaft 11′, 11″ and thelink shaft 58 can in this design preferably be done via gearwheels 209.A high gear ratio as shown in the figure is used for increasing therotation speed of the link shaft and decreasing the torque which givesless wear and smaller dimensions of the power transmission. In thisdesign only the drums 9 v, 9 h, 15′ are exposed to the sea water in thetransmission housing 20. The generator 21 with all belonging powerelectronics and the link shaft 58 including the power transmission areencapsulated in a climate controlled environment 195. The return feeding26 has in this design been placed on the high speed side of the gear 35,but could also be placed on the low speed side. One advantage withplacing the return feeding 26 on the high speed side is that the spacewill be used more efficiently since it requires a higher gear ratio inthe return feeding compared to the link shafts power transmission 210. Ahigh speed rotation in the slipper clutch gives higher transmissionlosses though.

In FIG. 15 i an alternative to return feeding, which is described inrelation to FIG. 15 g is shown. Here an electric motor 223 is usedinstead, which is directly connected to any of the gearwheels 209 on thelink shaft 58. The electric motor gets power from the battery, notshown, which drives the control system and other electronics, not shown.The electric motor is controlled by the control system which in that waycan optimize the return feeding. It is also possible to drive the returnfeeding by means of a spring mechanism, such as e.g. a coiled spring ora constant power spring, not shown.

A wave energy converter has here been described which can have one ormore of the following advantages:

-   The counterweight drum/drums limit the maximum resistance in the    system and give a sharp limit for the torque acting over the    generators.-   The energy accumulation is very simple and efficient and can store    energy over long time intervals at the same time as the motive force    can be held constant in relation to the average wave height during    the time interval.-   The wave energy converter can be dimensioned to utilize the depth on    the installation site in an optimal way for the accumulation and for    decreasing the weight of the counterweight.-   The storage of energy is stopped automatically when “the accumulator    is full” and this can be achieved without the generator losing    power.-   The scalability is very good and the wave energy converter can be    dimensioned to reach maximum capacity at a selected wave height to    get a better utilization factor of the generator.-   It is not necessary to over dimension the whole system to be able to    handle absorption of energy at rare occasions when the mean wave    height is considerably higher than normal.-   The buoy continuously follows the wave motions independently of how    large the waves are. The force limitation in the anchor drum    efficiently protects the device from thrusts and overloads.-   The motive force is constant in relation to the gear ratio which    enables the use of all types of generators, incl. synchronous AC    generators, which are working with constant or variable rotation    speed.-   Minimal manual efforts at installation, short course of installation    which generators electricity already when the foundation is being    lowered down.-   Mainly simple and durable construction.-   Very high utilization factor of the generator and transmission.-   Long service intervals.

While specific embodiments of the invention have been illustrated anddescribed herein, it is realized that numerous other embodiments may beenvisaged and that numerous additional advantages, modifications andchanges will readily occur to those skilled in the art without departingfrom the spirit and scope of the invention. Therefore, the invention inits broader aspects is not limited to the specific details,representative devices and illustrated examples shown and describedherein. Accordingly, various modifications may be made without departingfrom the spirit or scope of the general inventive concept as defined bythe appended claims and their equivalents. It is therefore to beunderstood that the appended claims are intended to cover all suchmodifications and changes as fall within a true spirit and scope of theinvention. Numerous other embodiments may be envisaged without departingfrom the spirit and scope of the invention.

1. A wave energy plant comprising: a buoy or other device arranged at orin a pool of water to be put into motion by motions of the water in thepool of water, a driveshaft, which is rotatably journalled in bearingsto the buoy resp. the other device or to a device arranged to give acounteracting force against the motions of the water in the pool ofwater, a first oblong organ, which in one end is coupled to a devicearranged to give a counteracting force against the motions of the waterin the pool of water resp. to the buoy and in the other end is coupledto the driveshaft, an electric generator, which is coupled to thedriveshaft and includes two in relation to each other rotatable parts, afirst part and a second part, and an energy accumulation device, atwhich the buoy or the other device is placed and the buoy or the otherdevice, the first oblong organ, the device arranged to give acounterforce against the wave motions, the driveshaft and the energyaccumulation device are coupled together, so that the coupling betweenthe first oblong organ and the driveshaft gets the driveshaft to mainlyat the first motions in the buoy or the other device, rotate in aunidirectional direction and thereby drive the electric generator's twomentioned parts to rotate in relation to each other in a firstrotational direction and generate electric current and thereby alsosupply the energy accumulation device with energy, characterized in thatwherein the energy accumulation device is arranged to mainly at thesecond motions, which are mainly separated from the first motions, inthe buoy or the other device, drive the electric generator's mentionedtwo parts to rotate in the same first rotational direction in relationto each other and thereby to generate electric current with the samepolarity as when the driveshaft drives the electric generator's twomentioned parts to rotate in relation to each other.
 2. A wave energyplant according to claim 1, comprising a buoy, which is arranged toalternately rise and sink and/or to alternately rock back and forth atthe up and down motions of the water surface, and the buoy, at which thefirst motions in the water surface includes either one of the up- anddown-going motions of the water surface.
 3. A wave energy plantaccording to claim 1, wherein the driveshaft is mechanically coupledwith the generator's first part, at which an electromagnetic couplingexists over an air gap between the electric generator's first and secondparts at least during these parts relative movements, and the energyaccumulation device is mechanically coupled to the second part of theelectric generator.
 4. A wave energy plant according to claim 3, whereinthe coupling of the energy accumulation device to the driveshaft via theelectric generator's second part and the electric generator's first partand the air gap between them gives a counteracting motive force, whichcounteracts the rotation of the driveshaft, when the driveshaft throughthe coupling between the first oblong organ and the driveshaft rotatesand drives the electric generator's first part, so that the electricgenerator's second part rotates in a first rotational direction throughthe coupling to the driveshaft via the electromagnetic coupling over theair gap and the electric generator's first part, when the motive forcewhich acts on the driveshaft through the coupling between the firstoblong organ and the driveshaft, exceeds the counteracting motive forceat which the energy accumulation device through its mechanical couplingto the electric generator's second part accumulates energy, at which theelectric generator's first and second parts at the same time rotates inthe same first rotational direction in relation to each other, and sothat the electric generator's second part is driven by the energyaccumulation device to rotate mainly in the same first rotationaldirection, when the motive force, which acts on the driveshaft throughthe coupling between the first oblong organ and the driveshaft, do notexceed the counteracting motive force, at which the electric generator'sfirst- and second parts is made to continue to rotate in the same firstrotational direction in relation to each other.
 5. A wave energy plantaccording to claim 1, comprising: a mechanical gear coupled between thedriveshaft and the electric generator's first part, at which thedriveshaft is coupled to the ingoing side of the mechanical gear and theelectric generator's first part is coupled to a first outgoing side ofthe mechanical gear, at which an electromagnetic coupling exists over anair gap between the electric generator's first part and second part atleast during their relative movements, the electric generators secondpart is fixed to the buoy, and the energy accumulation device ismechanically coupled to a second, from the first separated, outgoingside of the mechanical gear.
 6. A wave energy plant according to claim5, wherein the mechanical gear's ingoing side includes an ingoing shaftand one outgoing side of the mechanical gear includes an outgoing shaftand one other outgoing side includes a housing or casing for themechanical gear.
 7. A wave energy plant according to claim 1, comprisingan anchor drum, which is journalled in bearings for rotation in aunidirectional rotation around the driveshaft and is coupled to thefirst oblong organ to bring the anchor drum to rotate with the mentionedfirst motion of the buoy or the other device and thereby also bring thedriveshaft to rotate.
 8. A wave energy plant according to claim 7,wherein the first oblong organ is a flexible organ, a line, wire orchain in particular, which in one end is more or less winded up on ananchor drum, and that a mechanism exists for at the mentioned second ofthe buoy's or the other device's motions, rotate the anchor drum so thatthe flexible organ is kept in a stretched state.
 9. A wave energy plantaccording to claim 7, wherein the bearing for a unidirectional rotationof the anchor drum around the driveshaft, which enables the anchor drumduring rotation in the opposite direction to drive the driveshaft torotate in the opposite direction, includes a coupling for limitation ordisengagement of the motive force, with which the anchor drum herebyacts on the driveshaft.
 10. A wave energy plant according to claim 1,wherein the driveshaft is journalled in bearings at a buoy and that thefirst oblong organ in one end is coupled to a point which counteracts tothe buoy's motions, especially to a fixed point like at the bottom ofthe pool of water or to a fixed of fastened device at the bottom of thepool of water.
 11. A wave energy plant according to claim 1, wherein thedriveshaft is rotatably journalled in bearings to one at the pool ofwater fixed device and that the first oblong organ in one end is coupledto a buoy.
 12. A wave energy plant according to claim 11, wherein thedriveshaft is placed below the water surface and that the energyaccumulation device includes at least one floating body.
 13. A waveenergy plant according to claim 1, wherein the driveshaft is rotatablyjournalled in bearings to the buoy and that the first oblong organ inone end is coupled with a weight, which is resiliently suspended to thebuoy.
 14. A wave energy plant according to claim 1, wherein the buoyincludes a space, which functions as an air pocket and in which at leastthe main part of the driveshaft is located.
 15. A wave energy plantaccording to claim 1, wherein the energy accumulation device includes acounterweight arranged as a lead which moves upwards at the mentionedfirst of the buoy's or the other device's motions and at which potentialenergy is stored, that the coupling between the buoy or the otherdevice, the first oblong organ, the driveshaft and the counterweight isarranged in a way, that the counterweight moves downwards at thementioned second motion of the buoy or the other device and that thecounterweight drives the generator's first and second parts to rotate inrelation to each other in the first rotational direction.
 16. A waveenergy plant according to claim 15, wherein the energy accumulationdevice includes a counterweight drum rotatably journalled in bearings tothe driveshaft and a second oblong organ for coupling of motions in thecounterweight to drive the counterweight drum to rotate, at which thedriveshaft is coupled to rotate the electric generator's first part andthe counterweight drum is coupled to rotate the electric generator'ssecond part, at which the electric generator generates electric currentwhen its second part rotates in relation to its first part at the sametime as it gives a counteracting torque to this rotation, at which theelectric generator's first and second parts is brought to rotate inrelation to each other, always in the same first rotational direction.17. A wave energy plant according to claim 15, wherein the energyaccumulation device includes a counterweight drum rotatably journalledin bearings to the driveshaft and a second oblong organ for coupling ofmotions in the counterweight to drive the counterweight drum to rotateand that a mechanical gear is coupled between the driveshaft and theelectric generator's first part, at which the driveshaft is coupled toan ingoing side of the mechanical gear, the electric generators firstpart is coupled to an first outgoing side of the mechanical gear, theelectric generator's second part is fixed to the buoy or the otherdevice and the counterweight drum is mechanically coupled to a second,from the first separated, outgoing side of the mechanical gear, so thatthe driveshaft at the mentioned first motions in the buoy or the otherdevices gives motive forces on both outgoing sides of the mechanicalgear for rotation of the electric generator's first part and forrotation of the counterweight drum to hoist up the counterweight inrelation to the driveshaft and so that the counterweight drum at thementioned second motions in the buoy or the other device gives a motiveforce via its coupling to the gear's second outgoing side for rotationof the electric generator's first part.
 18. A wave energy plantaccording to claim 1, wherein the energy accumulating device includes acounterweight drum and a counterweight and that the second oblong organis a flexible organ, a line, wire or chain in particular, which in thelower end is fixed to the counterweight and its upper end is more orless winded up on the counterweight drum.
 19. A wave energy plantaccording to claim 1, comprising a control system for controlling theelectric generators electric load or field current for adjusting therotation speed between the electric generator's first and second parts.20. A wave energy plant according to claim 19, wherein the energyaccumulation device includes a counterweight or a floating body and thatthe control of the electric generator's electric load or field currentalso is used for adjusting the counterweight's resp. floating body'svertical speed, so that the counterweight resp. the floating body moveswithin an adapted or suitable vertical span at the motions of the buoyor the other device.
 21. A wave energy plant according to claim 20,wherein the control system is arranged to compensate for variations inthe torque, which is caused by the levy in mass of the counterweightresp. floating body, by regulation of the rotation speed between theelectric generator's first and second parts, which gives a continuouseven power output from the electric generator.
 22. A wave power plantaccording to claim 1, wherein it includes two electric generators andtwo belonging energy accumulation devices coupled to the driveshaft, atwhich the first oblong organ is coupled to the driveshaft to a placelocated between the two pairs of electric generator and belonging energyaccumulation device.
 23. A wave power plant according to claim 1,wherein the first oblong organ at least in one end includes two suborgans, at which a first sub organ is coupled to the driveshaft on oneside of the electric generator and another sub organ is coupled to thedriveshaft on the opposite side of the electric generator.
 24. A waveenergy plant according to claim 1, wherein it includes an anchor drumcoupled to the first oblong organ and that the first oblong organincludes a flexible organ, a line, wire or chain in particular, which atleast in one of its ends is divided into two sub organs, which each oneis more or less winded up on the corresponding wind up surfaces of eachanchor drum, at which the wind up surfaces have helicoidally runninggrooves with opposite helicoidal directions.
 25. A wave energy plantaccording to claim 1, wherein the energy accumulation device includestwo counterweight drums journalled in bearings to the driveshaft and aflexible organ, a line, wire or chain in particular, which at least inone of its ends is divided in two flexible sub organs, which each one ismore or less winded up around corresponding wind up surfaces on thecounterweight drums, at which the wind up surfaces has helicoidallyrunning grooves with opposite helicoidal directions.
 26. A method ofextracting electrical energy from more or less periodical motions of abody, especially repeated back and forth motions and/or repeated rockingmotions in two opposite directions, wherein that at the first motions ofthe body let these motions drive two parts of an electric generator torotate in relation to each other in a first direction and herebygenerate electric current and at the same time also supply an energyaccumulation device with mechanical energy, and that at the secondmotions of the body, which mainly is separated from the first motions,let the energy accumulation device drive the electric generators twoparts to rotate in the same first direction in relation to each otherand thereby generator electric current with the same polarity as at thefirst motions of the body.